Build the EM Theremin

This classic electronic instrument gives goodvibrations and excitations.

By Robert Moog

ost electronic musical instru-ments are sonic chameleonsthat try to sound like a widevariety of other things. How-ever, there is one electronicinstrument that makes no

lapologies for its single, immediatelyrecognizable sound: the theremin. Thismonophonic instrument has added itsdistinctive, melodic character to thescores of many horror and suspensemovies and made its pop debut on theBeach Boys' "Good Vibrations." It hasalso appeared on many concert stages,including Carnegie Hall.The theremin was named after its in-

ventor, Russian physicist and musicianLeon Theremin, who developed theinstrument in the 1920s. Unlike mostmusical instruments, the theremin isplayed with absolutely no physical con-tact. Players wave their hands in the airnear two antennas. As one hand getscloser to the straight vertical tube(called the pitch antenna), the pitchrises; as the other hand gets closer tothe horizontal tubular loop (called thevolume antenna), the volume decreases.Because the theremin's pitch andvolume are intimately tied to the play-i

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materials that you can buy at your localhardware store or from mail-orderelectronic-parts distributors. If youknow how to read a schematic diagram,solder, and use a voltmeter, and ifyou're comfortable with basic hometools, you should be able to build andadjust this theremin.

er's hand motions, the tone has avibrant, wavering quality, not unlike ahuman voice or a violin.

Among the requests for DIY projectsthat EM receives, by far the most com-mon is a do-it-yourself theremin. Theinstrument presented here is an au-thentic theremin, with antenna responsecharacteristics, pitch range, and tonecolor that closely emulate LeonTheremin's original designs. However,it is reasonably easy to build. It usescurrently available components and

OVERVIEWWhen you bring your hand near atheremin antenna, you are actuallyforming a variable capacitor: the an-tenna is one "plate" and your hand isthe other. With the high frequenciesand very low currents used by the in-strument, your hand is effectivelygrounded by being attached to yourbody, so the antenna and your handform a variable capacitor to ground.This variable capacitance is calledhand capacitance. You increase thehand capacitance by bringing yourhand nearer to the antenna. Duringnormal operation, the hand capacitanceis less than one picofarad, which is avery small capacitance indeed!

Each antenna forms a resonantcircuit with a group of inductorscollectively called an antenna coil. Inthis design, the resonant frequenciesare about 260 kHz for the pitchantenna and about 450 kHz for thevolume antenna. At or near theresonant frequency, a tiny change inhand capacitance results in a largerchange in the impedance of theantenna circuit as a whole.Refer to Figure 1, the functional block

diagram, and Figure 2, the schematic dia-gram of the entire circuit. The variable-pitch oscillator (VPO), fixed-pitch oscillator(FPO), and detector sections form a beat-frequency oscillator. Q1, Q2, and theirassociated components constitute theVPO, the frequency of which is set

The theremin's main circuitry is mounted on a single prototyping board, and the two antennacircuits are mounted on their own smaller boards.

to make fine adjustments to the vol-ume-oscillator frequency duringperformance.The audio waveform is applied to pin 3

of U3-A at a level high enough to clip it.This has the effect of reshaping thewaveform from a skewed sine to a quasi-rectangular wave, which is very similar to the waveform of Professor Theremin'soriginal instruments. P3 varies the inputresistance of U3-A, which influences theamount by which the audio waveform isclipped. P4 shifts the bias at the input ofU3-A, which changes the waveform widthand therefore the output's harmonicspectrum. C24 and C26 roll off thehigh-frequency harmonics to produce apleasant, cello-like tonal balance.

ANTENNASMaking the antennas can be tricky.They should be metallic, rugged,attractively finished, capable of beingrigidly mounted, and easy to fabricateby a home hobbyist. I have found that3/8-inch soft copper tubing of the sortthat plumbers use with bathroom sinksworks well. You can buy preplated,straight, short pieces at your localbuilders' supply or hardware store. Youcan also purchase a simple tubingbender that will allow you to bend thevolume antenna by hand withoutcollapsing the tubing. You'll also need atubing cutter or hacksaw to cut thetubing to length.

The finished pitch antenna is astraight, vertical tube eighteen incheslong and 3/8 inch in diameter, and thefinished volume antenna is a horizon-tal, hairpin loop with a total length ofnine inches. The ends of the volume

FIG. 1: This functional block diagram reveals how the theremin works.

the DC voltage appearing at the junc-tion of D1 and C12 is reduced. The re-sulting current flowing through R14 isamplified and level-shifted by the VCAprocessor section (U3-B and associatedcomponents) and then fed throughR30 to control the gain of the voltage-controlled amplifier (U3-A and associatedcomponents). The amplitude-con-trolled audio output is then fed tofront-panel jack J1. The maximum levelis about 0 dBm (0.8V RMS).

Q8 and its associated componentsconstitute the volume-tuning circuit,which is nearly identical to thepitchtuning circuit. Potentiometer P2 isused

slightly higher than the resonant fre-quency of the pitch-antenna circuit (es-tablished by adjusting L5). As a playerbrings a hand near the pitch antenna,the changing impedance of the pitchantenna circuit lowers the VPOfrequency by about 3 kHz.

Q3, Q4, and their associated compo-nents form the FPO, the frequency ofwhich is set equal to the VPO frequen-cy (by adjusting L6) when the player'shand is away from the pitch antenna.The difference, or beat, frequency isextracted by the detector and appearsas an audio waveform at the junction ofR23 and R24. As the player brings ahand near the pitch antenna, thefrequency of the audio waveform goesfrom 0 to about 3 kHz (3½ octavesabove middle C).Q5 and its associated components

constitute the pitch-tuning circuit. Thiscircuit presents a variable active im-pedance that is used to make fine ad-justments to the FPO frequency whilethe instrument is being played. Front-panel potentiometer P1 adjusts the cur-rent through Q5, thereby changing itsactive impedance.

Q6, Q7, and their associated com-ponents form the volume oscillator. Itsfrequency is set slightly higher than theresonant frequency of the volume-antenna circuit by adjusting L11. As theplayer brings a hand near the volumeantenna, the resonant frequency of thevolume-antenna circuit is lowered, and

The EM theremin closely emulates Leon Theremin's original design, although it is housed in asmaller cabinet.

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CABINETThe entire cabinet is made of wood.Except for the front panel, large metalcabinet parts should not be used, asthey may add unnecessary capacitanceto the antennas. My materials of choiceare hardwood plywood for the top andsolid hardwood for the rest of thecabinet because they are rugged, easyto shape accurately, and can be attrac-tively finished.The enclosure consists of a base and

cover (see Fig. 3). The cover should fitsnugly over the base. You may fastenthe pieces together with anycombination of nails, wood screws, andwood glue, depending on how you liketo put cabinets together. After thecabinet parts have been assembled, sandthem down well and finish them withthe wood finish of your choice, exceptmetallic paint.

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antenna should be separated by 3¼inches, center to center.

I suggest you make the antennaslonger than necessary and then cut themto length after they're formed andstiffened (discussed shortly). Start witha straight, 24- or 36-inch length oftubing for each antenna. To form thevolume antenna, slip the tubing benderover the tube. Then, starting ,at themidpoint of the tube, bend it into asemicircular curve. Hold the tube inboth hands and push into the curve withyour thumbs while pulling down withyour other fingers. Doublecheck tomake sure that the two ends of thevolume antenna are parallel and are thecorrect distance apart.

Copper tubing has one drawback: be-cause copper is soft enough to bend byhand, it is easy to put unwanted kinksin the tubing after it has been formed.You can stiffen the antennas by fillingthem with polyester resin (the liquidplus-hardener type used to repair carbodies) after you've formed them. This

is not particularly difficult, but the po-tential for making a mess is significant,so be sure you have plenty of time andyou're at peace with the world.

The pitch antenna is straight becausethis configuration is more sensitive tochanging hand position when the handis farther away and less sensitive whenthe hand is close. The change in handcapacitance is extremely small whenthe hand is far away, and the change inpitch as a function of distance must beas uniform as possible.

The volume antenna is loopedbecause this configuration is less sen-sitive when the hand is far away andmore sensitive when the hand is close.This gives you greater control over thelow end of the dynamic range and letsyou articulate notes by quickly dippingyour left hand into the loop (more in amoment)

The two antennas are perpendicularto each other to minimize the interac-tion between them. For example, asyou move your left hand tip and down

above the volume antenna, its motion isparallel to the pitch antenna, whichcauses little or no change in pitch.

FIG. 2: The schematic for the EM theremin.

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The antenna sockets are regulartube-to-pipe connectors that you can getwhen you buy the copper tubing for theantennas. The volume-antenna socketsare straight 3/8-inch-tube-to-3/8-inch-male-pipe connectors, whereas thepitch-antenna socket is a right-angle,3/8-inch-tube-to-3/8-inch-male-pipeelbow. Drill 3/8-inch holes for thesefittings; then screw them in by hand. Ifyou can't screw the 3/8-inch pipethreads into the wood by hand, don'tforce it by using a pipe wrench: youmay split the wood. Instead, enlarge thehole slightly with a large round file or a3/8-inch pipe tap.

Once you're sure you can screw in thepipe fittings by hand, unscrew them,put a small amount of epoxy on thethreads, and reinsert them by hand.Before the epoxy hardens, verify thatthe pitch-antenna socket is vertical byinserting the pitch antenna into thesocket and adjusting the position of thesocket as necessary.

Two 4/4-inch X 3/4-inch blocks andone microphone-stand mounting flangeare attached to the bottom of the enclo-sure. This lets you set the finished uniton a microphone stand (preferred) or ona wood (not metal) table when you playit.

FRONT PANELThe front panel should be made of1/16-inch sheet aluminum. It should beabout nine inches long and should havebends at the top and bottom formounting and stiffening. You can ei-ther cut and bend the panel yourself orhave your local sheet-metal shop do itfor you. Alternatively, you can buy ablank, single-space (1U) rack panel,which is 1¾ inches high by nineteeninches wide, cut it to length with ahacksaw, and attach the panel to thebase from the front instead of from thebottom. However, that will leave a1/4-inch gap between the top of thepanel and the enclosure cover.Four rotary potentiometers, one

1/4-inch phone jack, one 1/8-inch mini-jack, and one toggle switch are mount-ed on the front panel. The two tuningpots should be located in the left part ofthe panel so your hand is as far from thepitch antenna as possible when Youtune the antennas. Use high-quality,full-size rotary pots and large-diameterknobs for PI and P2, P3 and P4 are lesscritical; these pots can be miniature,and the knobs can be small. I suggest

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you use an insulated, 1/4-inch jack forJ1 to avoid a ground loop between theaudio and power grounds.

Eight single-conductor wires and oneshielded wire connect the front-panelcomponents to the main circuit board, Isuggest you use a connector for thesewires so Von can unplug the panel ifyou need to work on the main circuitboard. Prototyping boards often haveprovisions for mounting a DB15 orDB25 connector.

MAIN CIRCUIT BOARDAll circuitry (except the antennacircuits and front-panel components) ismounted on one circuit board (see Fig.4). A plug-in prototyping board of the

THEREMIN: AN ELECTRONIC ODYSSEY

sort used to assemble computer I/Ocircuits provides the space, connectionprovisions, and solidity you need.Radio Shack's prototyping board(catalog #276-1598) provides amplespace for all the circuitry with extraroom to try your own modifications.

The theremin's power is supplied by a±12 VAC wall wart, which is widelyavailable (see sidebar "Where to GetParts and Materials"). The AC voltageis converted into DC by two voltageregulators (UT, U2, and associatedcomponents). Keep the power-supplycircuit components as close together aspossible, and keep connections asshort as you can. Be really sure that

Leon Theremin lived a long, produc-tive, and amazingly diverse life. Hedeveloped the theremin during the1920s, a time when most people hadnever even heard of radio! He camefrom Russia to New York City in 1927and instantly became the darling ofthe cultural elite. He set up alaboratory and studio in mid-town Manhattan, where hedeveloped new instrumentsand tutored a long string ofstudents. His greatest protegewas Clara Rockmore, ayoung Russian musician whowas originally trained as aclassical violinist.

Professor Theremin'stenure in the United Statescame to an abrupt end oneday in 1938, when he wastaken back to Russia by So-viet agents under circum-stances that are still not fullyknown. For decades after

Clara Rockmore was Leon Theremin's greatest protege

Theremin disappeared, nobody in the An amazing array of peopleWest knew of his whereabouts. Some appear in the film, including Brianpublications even reported that Wilson of the Beach Boys (talkingTheremin had died in a Soviet prison about the use of theremin induring the Second World War. For- "Good Vibrations"), Clara Rockmore,tunately, the rumors of his demise Jerry Lewis, and Todd Rundgren (dowere premature; Theremin actually ing an on-camera imitation of thesurvived until 1993. theremin). In addition, I discuss the

A few years ago, documen- technical side of theremins at severaltary filmmaker Steven Martin (not the points in the film. But most impor-comic actor) became interested in tant, the true story of Leon ThereminTheremin's story. He interviewed is told in a way you won't forget.people who had known Theremin, -Robert Moog

located old newsreels and homemovies, and dug deep into the life ofthis amazing man. The result is afilm entitled Theremin: An ElectronicOddessy. If you haven't alreadyseen this movie, watch for it at yourneighborhood cinema.

that C20 and C22 are very close to U2.The negative side of C19 and the posi-tive side of C20 should be connectedtogether with a very short lead, and thegrounded side of J2 should also beconnected to this lead. The voltageregulators are less likely to oscillate ifthe connections are kept as short aspossible.

Be sure to separate the VPO from theFPO by a couple of inches. These os-cillators are already lightly coupledthrough C2 and C6, so they tend tosynchronize at low beat frequencies(which is desirable). Placing the oscil-lator circuits close together increases thecoupling, which may result in anexcessive tendency to synchronize. Inaddition, place C4, C8, and C13 veryclose to the oscillator circuits withwhich they are associated to maximizethe decoupling.

After the main board is assembled andchecked, brush the solder side with asmall wire brush and inspect for un-wanted solder bridges, wiring mistakes,and weak solder joints. Then set theboard in the middle of the cabinet basein preparation for final test and tuning.

FIG. 3: Fabricating the cabinet requires some basic woodworking skills.

ANTENNA CIRCUIT BOARDSThe inductors and other antenna-cir-cuit components are mounted on twoseparate, small circuit boards with lit-tle or no copper circuit pattern. LIthrough L4 are mounted on the pitch-antenna circuit board (see Fig. 4). Po-sition the inductors so they areparallel to one another and about oneinch apart, center to center. Theinductors are not polarized per se, buteach terminal is distinct: one emerges

from the center of the coil and theother emerges from the outer layer ofthe coil. Arbitrarily select one terminalas the beginning and the other as theend, and connect the inductors in se-ries so the end of one inductor isconnected to the beginning of the next.

Position the board on the base next tothe pitch antenna. The free end of L4should be close to the main circuitboard, and the free end of Ll should beclose to the pitch-antenna socket.

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Connect a short wire from the free endof LI to the pitch-antenna socket usinga heavy soldering iron or by drillingand tapping a hole for a 4-40 threadand then mounting a solder lug.

L7 through L10, DI, C12, and R14are mounted on the volume-antennacircuit board (see Fig. 4). As with the

pitch-antenna circuit, position theinductors so they are parallel to oneanother, about an inch apart, and con-nected so the windings are end to be-ginning. Position the board near thevolume antenna, and install wires toconnect the free end of L10 to the vol-ume-antenna socket. In addition, con-

nect the junction of L7 and C12 to thejunction of C14 and C15, and connectthe free end of R14 to pin 13 of U3.

CHECKING IT OUTAfter you've assembled and cleanedthe main board, take a deep breath andcheck all your connections again. Look

PARTS LIST

Integrated CircuitsU1 LM781L12 12V positive regulator

U2 LM79L12 12V negative regulato U3 LM1360ON dual operational

transcondance amplifier(National Semiconductor)

Transistors Q1-Q8 2N3904 NPN

DiodesD1, D4, D5 1N4148 signal diode

D2, D3 1N4001 power diode

Capacitors C I, C5 3,900 pF/50V, 5%, polypropylene

or polystyrene C2 C6, C 16 22 pF/50V, 5%, NPO (zero

temperature coefficient) ceramic C3, C7, C15, C26 0.01 µF/50V, 10%, polyester

C4, C8, C1O, C11 1.0 µF/35V tantalumC13, C17, CI8, C25 1.0 µF/35V tantalumC9 33 µF/50V, 5%, NPO (zero

temperature coefficient) ceramic C12 1,000 pF/50V, 10%, ceramic

C14 2,200 pF/50V, 5%, polypropyleneor polystyrene

C19, C20 2,200 µF/35V aluminumelectrolytic

C21, C22, C27 0.1 µF/5OV ceramicC23 4,700 pF/50V, 10%, ceramicC24 3,300 pF/50V, 10%, ceramic

InductorsL1, L2, L3, L4 10 mH, 3-section, RIF choke

(J. W. Miller #6306) L5, L6 100 pH, hi-Q, variable inductor

(Toko RWRS-T1015Z)L7, L8 2.5 mH, 3-section, RIF choke

(J. W. M i ller #6302)L9, L10 5 mH, 3-section, RF choke

(J. W. Miller #6304)L11 68 µH, hi-Q, variable inductor

(Toko 154ANS-T1019Z)

Potentiometers P1, P2 5 kΩ linear taper, cermet or

conductive plastic (Clarostat 53C1-5K or equivalent)

P3 P4 50 kΩ linear taper

Resistors (¼¼¼¼W, 5%, metal or carbon film)R1, R4, R5, R8 1 kΩR2, R6, R13, R16, R21 2.2 kΩR3, R7, R30 ,R38 47 kΩR9, R12, R22 10 kΩR23, R39, R40 10 kΩR10, R15, R17, R19 470ΩR11, R20 33ΩR14 560 kΩR18 2.7 kΩR27, R29 100 kΩR24 R26, R31 4.7 kΩR32, R33, R34 4.7 kΩR25 330 kΩR28 150 kΩR35, R36 1.8 MΩR37 4.7 MΩ

Switch SW1 SPST miniature power switch

ConnectorsJ1 Insulated ¼-inch phone jack

(Switchcraft N-1 11 or equivalent)J2 3.5 mm phone jack (Switchcraft

41 or equivalent)

Parts Not on Schematic• 16-pin IC socket for U3• Connector set with at least ten conductors for connections

between the main circuit board and front panel• Wall-wart transformer to provide 12 to 15 ILIAC with at least

200 mA (Cui-Stack DPA120020-P1-SZ)• Two large knobs for PC and P2• Two small knobs for P3 and P4• Two 24- to 36-inch x 3/8-inch straight copper tubes for

antennas• Tube bender for volume antenna• Atlas AD-11 B microphone-stand mounting flange• 10-inch x 4-inch prototyping circuit board• Two 4-inch x 3-inch prototyping boards for the antenna

circuits

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for shorts, mistakes, missing connec-tions, etc. Then connect the front panelto the main board, plug in the powersupply, and turn the power switch on.

Use a voltmeter to check the voltagesat the inputs and outputs of U1 and U2(see Fig. 2). Then check the DCvoltages at the collectors of Q1 throughQ8 (they should all be about +12V); theemitters of Q1 through Q4, Q6, and Q7(about 0.6V); and the emitters of Q5and Q8 (about -2.6V). If you don'tobserve all these readings, checkeverything until you find the problem.

Next, verify that all three oscillatorsare working. Read the AC voltagesacross L5, L6, and L1 I. If you readabout 10 VAC, then the correspondingoscillator is producing a waveform. Ifyou don't read any voltage at all, the

oscillator is not working. To check thedetector, measure the DC voltageacross R24. If it's -0.5V or so, thedetector is working.

Temporarily connect a pair ofheadphones or a small powered speakeracross R24. Turn the tuning slugs in L5and L6 counterclockwise until the topsof the slugs hit the shield cans. Becareful. Do not force the slugs fartherthan they want to go! Turn L5 exactlytwo turns clockwise. Then turn L6clockwise slowly until you hear a high-pitched whistle. Keep turning until thetone is in the mid range (about I kHz).Now, turn P1 in either direction. Youshould hear the pitch change markedly.If you observe all these things, then theentire beat-frequency oscillator circuitis in good shape.

To check the VCA, temporarilyconnect pin 12 of U3 to ground. (Thisshould turn on the VCA.) Connectyour headphones or monitor ampacross R34. You should hear a some-what louder tone. Now, disconnect thetemporary ground connection to pin12 of U3, and connect that pin to -12V.The audio across R34 should disappear.If it does, the VCA is working properly.

While pin 12 of U3 is connected toground, you can also check the Bright-ness and Waveform controls (P3 andP4). Use the Pitch Tuning control (PI)to set the tone's pitch to approximatelymiddle C. Then turn the Brightness andWaveform controls. The Brightnesscontrol should change the sound frommuted to bright, and the Waveformcontrol should change the sound

FIG. 4: The position of certain components is critical to minimize unwanted oscillations and capacitances

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from “reedy” (narrow waveform) to“full” (wider waveform). After youhave checked all of these controls,remove the temporary connection topin 12 of U3.

TUNINGBefore tuning, clean off your work-bench and move aside any large, con-ductive objects such as desk lamps andtest gear. Leave a clear space of two orthree feet around your work area. Placethe cabinet base in the middle of thecleared space, put the pitch antenna inplace, and connect the pitch-antennacircuit board between the antenna andthe main board. On the main board,temporarily connect pin 12 of U3 toground and connect the instrument'saudio output to headphones or amonitor amplifier. Now follow thesesteps to adjust L5 and L6:

1. Set PI (the Pitch Tuning control)to its middle position.

2. Grasp and hold the pitch antennawith one hand. With the other hand,adjust L6 until the beat frequency iszero, Then carefully turn L6 counter-clockwise until you hear a pitch of about

3 kHz (3 ½ octaves above middle C).3. Let go of the pitch antenna. Slowly

retract your hand from the vicinity ofthe antenna. You should hear the pitchgo down.

4. If the pitch does not go down to

zero when you've retracted your handcompletely and stepped back, the in-ductance of L5 is set too high. Advancethe slug in L5 clockwise by a smallamount, perhaps 1/10 turn or so, andrepeat steps 2 and 3.

WHERE TO GET PARTS AND MATERIALSMost of the electronic parts for thisproject can be purchased from DigiKey(tel. 800/344-4539 or 218/681-6674; fax218/681-3380; Web http://www.digikey.com). Other suppliersinclude Allied (tel. 800/433-5700 or817/595-3500; fax 817/595-6404; BBS800/433-5003; Web http://www.allied.avnet.com), Mouser (tel. 800/346-6873 or817/483-4422; fax 817/483-0931), andNewark (tel. 800/463-9275 or 312/784-5100; fax 312/907-5378). RadioShack is a good place to shop forprototyping boards. You should be ableto get wood for the cabinet and all thematerials to make the antennas at yourlocal hardware superstore.

A complete kit and many of theindividual parts are available from BigBriar, Inc. (tel. 800/948-1990 or704/251-0090; fax 704/254-6233; emailbigbriar@aol.com). The kit includes anassembled and tested circuit board (withantenna circuits), completely fabricatedfront panel and antennas, and precutcabinet parts. Also included are TheComplete Theremin Video starring LydiaKavina, Clara Rockmore's The Art of theTheremin CD, and Bob Moog's detailedand illustrated booklet on theremintechnology and history. The price of thekit is $229, including shipping within theUnited States.

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5. If the pitch goes to zero and thenbegins to ascend as you retract yourhand, the inductance of L5 is set toolow. Turn the slug in L5 counterclock-wise by a small amount, and repeatsteps 2 and 3.

6. If the pitch jumps abruptly as youretract your hand, the inductance of L5is set far too low. Turn the slug in L5counterclockwise approximately aquarter-turn and repeat steps 2 and 3.

Eventually, you will converge on theproper settings for L5 and L6. The ideais to find the settings at which the fre-quency (a) is zero when you've steppedaway from the theremin, (b) begins toascend when your body is about twofeet from the pitch antenna, and (c)reaches about 3 kHz when your handtouches the pitch antenna. Tap lightly onL5 and L6 as you converge on theproper settings, which will stabilize thetuning-slug positions.

This completes the tuning of the pitchoscillators. In performance, the exacttuning is established by adjusting thepitch-tuning control (P1).Now, remove the temporary ground

connection to pin 12 of U3. Connect avoltmeter from pin 12 of U3 to ground,install the volume antenna, and connectthe volume-antenna circuit card betweenthe antenna and the main board. Followthese steps to adjust L11:1. Set P2 to its mid position.2. Carefully turn the slug in L11 coun-

terclockwise until it is out as far as it willgo. The meter should read about -12V.

3. Slowly turn the slug clockwise. Atsome point, you will see the voltagebegin to rise from -12V. Stop when thevoltage passes through 0 and becomespositive, At this point, bringing yourhand near the volume antenna lowers thevoltage; the meter should read about-12V when your hand is two or threeinches from the volume antenna.

This completes the tuning of the vol-ume oscillator. In performance, the exactvolume is established by adjusting thevolume-tuning control (P2).

PLAYING THE THEREMINYou are now ready to try your theremin.Place the instrument (with antennasinstalled) on a microphone stand that isset about 40 inches high. Connect asmall monitor amplifier and speaker to JI and the 12 VAC wall-wart poweradapter to J2. Turn on SW1 and touchthe pitch antenna. Set P2 so the tone isloud when your left hand is well away

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from the volume antenna and thevolume begins to decrease noticeablywhen your left hand is brought withinten to twelve inches of the volumeantenna. Then set PI so the frequency iszero when your right hand is well awayfrom the pitch antenna and the tonebecomes apparent when you bring yourright hand within 18 to 24 inches of thepitch antenna. Your instrument is nowready to play.

As with any expressive musicalinstrument, playing the theremin takessome practice. You can start by follow-

ing these simple exercises:1. Stand slightly left of the center of

the instrument with your right shoulderabout 24 inches from the pitch antenna.Relax your wrists. Think of a note andhum it to yourself. Then move yourright hand toward the pitch antennauntil the theremin pitch coincides withthe pitch you're humming. Now holdthe note. This is not as easy as itsounds, but it's an important techniqueto learn. At first, you will find itdifficult to stand still, but a few hoursof practice will work wonders.

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2. Hum two different notes, one afterthe other. Find the first note on thetheremin, hold it, and then slowlyglide to the second note.

3. Repeat the above exercise, butbring your left hand near the volumeantenna while your right hand glidesfrom one note to the next. Move theleft hand slowly at first and then morerapidly as you learn to move your lefthand independently of your right hand.This exercise teaches you to "feel"where the notes are and to impartexpressive dynamics.

4. While playing a note, introducevibrato by moving your right handback and forth from your wrist severaltimes a second. Concentrate on makingthe vibrato even and steady.

These exercises address the basicskills of theremin playing: findingnotes, playing intervals, articulatingnotes, and introducing vibrato. Withthese basic skills, you can play slowmelodies. Practicing regular scales andarpeggios will increase yourproficiency. Focus on accuracy of pitchand precise control of dynamics.

Once you've mastered the basicmoves, it's time to develop your ownstyle. Pay particular attention toshaping envelopes and dynamics withyour left hand. The left hand can alsobe used to articulate discrete notes bymomentarily dipping into the volumeantenna as the right hand quicklymoves from one pitch to another. Trycombining audible glides and discretepitch changes within a musical phrase.In addition, avoid constant vibrato inthe right hand. Instead, impartexpressive nuance by shaping theamount and rate of vibrato. Theseconsiderations are importantcomponents of theremin musicianship.The theremin presented here is

designed to meet the needs ofmusicians who wish to explore theartistic resources of this uniqueinstrument. Build your instrumentcarefully, and it will provide manyyears of reliable service. Practice withdiligence, and you will provideenjoyable music for yourself and youraudiences. Finally, be sure to give anoccasional thought to the spirit of LeonTheremin, to whom we owe so much.

Robert Moog was a pioneer in the early de-velopment of commercial synthesizers andcurrently serves as Grand Poobah of BigBriar, Inc.

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