Theremin
It only sounds while you don't touch it — your hand is one plate of a capacitor
Related
Over a hundred instruments are done in this section, and every one of them sounds by being touched:
strings pressed, holes closed, skins struck, reeds blown.
Only this one sings better the less you touch it.
「人体是电路的一部分。你不需要按键或拨弦——你本人就是一个可变电容器。」
⭐⭐ This page is the theremin — the starting point of the electronic section. One line: your body is part of the circuit.
| Class | Assignment |
|---|---|
| HS class | Electrophone（oscillators, no acoustic primary vibrator）· continuous pitch（no frets, keys or stops）· contactless — ⭐ the youngest HS category（the fifth, added for instruments like this） |
| Origin | ⭐⭐ 1920, by the Russian physicist Léon Theremin, as a by-product of proximity-sensor research — the prototype was a wireless motion-detection alarm |
| Three firsts | ⭐⭐ patented 1928 · put into production by RCA in 1929 — the first commercially available electronic instrument · conceived from the start as fully electronic（before every electromechanical instrument） |
| Bayin note | The Zhou bayin predates it by three millennia — it was born three thousand years later |
⭐⭐ The main line: the hand is a plate, the air is the dielectric
The physics stands in one sentence:
Your hand and the antenna are the two plates of a capacitor; the air between them is the dielectric. Capacitance grows as the distance shrinks（C ≈ ε₀·A/d）.
⭐⭐ The hand moves → the capacitance changes → the frequency changes.
Two antennas, two jobs:
| ⭐ vertical antenna（right hand） | ⭐ horizontal loop（left hand） | |
|---|---|---|
| Controls | pitch | volume |
| Hand nearer | ⭐ pitch rises | ⭐ volume falls, to silence |
| Hand away | pitch falls | volume opens |
⭐⭐ Why the left one is a loop: 「环形让乐器对环上方与环内的垂直移动特别敏感 → nuanced dynamics, 甚至瞬间静音，用直觉的手势就能做」— ⭐ a volume pedal with no moving parts.
⭐⭐ You never hear the oscillators — you hear their difference
The most counter-intuitive part, and the most beautiful:
The pitch side runs two oscillators: one fixed（about 170–500 kHz, far above audio）, one variable（an LC resonant circuit with the antenna wired across the capacitor）. ⭐⭐ the audio output is the difference of the two frequencies.
「若固定振荡器 170 000 Hz、可变振荡器 170 440 Hz， 差频 440 Hz 就是一个 A4。」
⭐⭐ The frequencies the instrument itself produces are inaudible; what you hear is the gap between two inaudibles. （The trick is heterodyning, invented for early radio — ⭐ an instrument borrowed radio's ear.）
⭐⭐ It was not born an instrument
「1920 年，俄国物理学家列夫·捷尔明在研究接近传感器时注意到，自己靠近振荡电路时，身体的移动会改变音高。」
⭐⭐ His two earlier projects: 「早期的无线运动检测报警系统」and「气体密度/介电常数测量装置」— both were studies of capacitance in circuits.
⭐⭐ From alarm to instrument: one 「notice」 apart. （Compare this section: the dizi from bird-luring tools, the xun from a hunting stone — ⭐ an instrument's ancestor is often not an instrument, but a moment of finding it fun.）
⭐ Its first names: etherophone · thereminvox — ⭐⭐ 「以太 / aether」records what people imagined about sound travelling through air.
⭐⭐ The hardest instrument to play in tune
「没有品、没有键、没有任何音挡——每个音高都以连续场的形态存在于右天线周围，没有任何物理反馈告诉你音在哪里」.
⭐⭐ Masters rely on muscle memory: 「Clara Rockmore（who worked with Léon Theremin directly）为手的位置建立了精确的肌肉记忆；现代演奏者走同一条路——把乐器的空间地图内化」.
⭐⭐ Against this section: the niutuiqin hands one post to the player; the theremin hands the whole pitch field — ⭐ the hand's position in the air is the fingerboard, and the fingerboard is invisible.
⭐⭐ The 「alien」 sound: where it gets hired
Its sound 「被描述为像小提琴，但更诡异、更超凡」，tied to「外星 · 超现实 · 怪诞」glissandi.
⭐⭐ Its film résumé: 《爱德华大夫》（Spellbound, 1945）·《失去的周末》· 《地球停转之日》（1951）·《火星人玩转地球》·《爱德·伍德》— ⭐ the「cosmic」sound of the screen is usually this one.
⭐ Rock: Beach Boys（*Good Vibrations*）· Led Zeppelin · Radiohead. ⭐ Classical: Henry Cowell · Edgard Varèse wrote for it; ⭐⭐ Shostakovich was among the first to orchestrate it（the 1931 film *Aldna*）— a laboratory instrument entered the symphony.
⭐⭐ Form: one swap, then it stayed
「第一台原型是一只木箱装电子电路 + 一根垂直天线控音高 + 一个踏板控音量；捷尔明很快把踏板换成了水平环形天线——即今天通行的形制」.
⭐⭐ A century on, the form barely moved — 「1920 年代电路全用真空管；现代设计用运放与 CMOS 振荡器 IC——原理完全相同，元件只是更小更稳」. ⭐ The instrument found its shape at birth.
Recap: three sentences on the theremin
| Q | A |
|---|---|
| ⭐ The key point | ⭐⭐ your body is part of the circuit — hand and antenna are the plates of a capacitor（C ≈ ε₀·A/d）; ⭐⭐ it sounds by not being touched — the only one here |
| ⭐⭐ Two antennas | ⭐ vertical（right）= pitch（nearer rises）· ⭐ loop（left）= volume（nearer fades to silence）; ⭐⭐ the loop's shape is sensitive to vertical motion — dynamics and instant silence by gesture |
| ⭐⭐ How it sounds | ⭐⭐ heterodyne: audio = fixed − variable oscillator（170 000 − 170 440 = 440 Hz = A4）— ⭐⭐ you hear the gap between two inaudibles; the oscillators run far above hearing |
| ⭐⭐ Origin | ⭐⭐ 1920 · Léon Theremin · a by-product of proximity-sensor research（prototype = wireless motion alarm）→ patent 1928 → RCA 1929: the first commercial electronic instrument |
| ⭐⭐ Hardest to tune | ⭐⭐ no frets, keys, stops, no physical feedback → every note from muscle memory（Clara Rockmore, who worked with Theremin）; ⭐ the hand's position in the air is the fingerboard, and the fingerboard is invisible |
| ⭐⭐ Sound label | ⭐⭐ 「像小提琴，但更诡异、更超凡」 — alien, surreal, eerie; films: The Day the Earth Stood Still · Spellbound · Mars Attacks!; rock: Beach Boys · Led Zeppelin · Radiohead |
| ⭐ Classical | Cowell · Varèse wrote for it; ⭐⭐ Shostakovich orchestrated it early（1931, *Aldna*） |
| ⭐ Form history | prototype「box + vertical antenna + pedal」→ ⭐ pedal replaced by the loop, then it stayed; vacuum tubes → op-amps/CMOS, principle unchanged |
| ⭐⭐ Electronic section | the starting point of the electronic section — 「合成器的先声」: sound from electricity, shaped by voltage begins here |
| HS | Electrophone — the fifth HS category, added later for instruments like this |
Every other instrument keeps its music on paper; the theremin keeps its in the air.
⭐⭐ When the player's hand moves, what changes is not a string, a hole or a skin — it is the capacitance of the player's own body.
⭐⭐ This was the first such instrument; the whole electronic section that follows walks out of this one step.
特雷门琴属电鸣乐器（电子振荡发声，外差取差频）。音高连续无级——没有品、键或挡，音域理论上是连续场，实用演奏区约四至五个八度，此处以常用区 C2–E6 示意。右手距垂直天线的距离决定音高（越近越高），左手距水平环的距离决定音量（越近越轻）。没有物理参照点，每个音都靠肌肉记忆。记谱即实音（正弦类波形）。
Listen in the library
All tracks from midicn-lib — inline badge is the license tier (C1 commercial / C2 non-commercial / C3 study only).
Sources
- ⭐⭐ 主线：你的身体是电路的一部分（本页最该记住的一条） —— 「人体是电路的一部分。你不需要按键或拨弦——你本人就是一个可变电容器」：手与天线构成电容器的两块极板，中间的空气是电介质；「电容随距离 d 的减小而增大」（C ≈ ε₀·A/d）→ ⭐⭐ 移动的是手，改变的是电容量，听见的是频率 —— 全站所有乐器里，只有这一件靠「不碰」发声
- ⭐⭐ 出身是一台报警器（发明的意外性）：「1920 年，俄国物理学家列夫·捷尔明（Léon Theremin）在研究接近传感器时注意到，自己靠近振荡电路时身体的移动会改变音高」；「他此前开发了早期的无线运动检测报警系统与气体密度/介电常数测量装置——两个项目都在探索电路中的电容变化」→ ⭐⭐ 从报警器到乐器，中间只隔一次「注意到」；⭐ 「最初 marketed 为 etherophone（以太琴）与 thereminvox」
- ⭐⭐ 两根天线各管一件事：「垂直天线（右手）控音高——手越近音越高，越远越低；水平环形天线（左手）控音量——手越近音量越小，直到无声」；⭐⭐ 音量天线做成环形的理由：「环形让乐器对环上方与环内的垂直移动特别敏感 → 演奏者能用直觉的手势做出细腻的力度变化，甚至瞬间静音」—— ⭐ 左手那只环，就是一只没有机械部件的音量踏板
- ⭐⭐ 发声原理：外差（把两支看不见的振荡器相减）：「音高侧用两个振荡器——固定频率（约 170–500 kHz，远超音频）与可变频率（LC 谐振回路，天线并联在电容上）；音频输出 = 两振荡器频率之差」——「若固定振荡器 170 000 Hz、可变振荡器 170 440 Hz，差频 440 Hz 就是一个 A4」→ ⭐⭐ 乐器本身发出的频率你根本听不见；你听见的是两个「不可闻」之间的差
- ⭐⭐ 商业史的三个「第一」：「1929 年由 RCA 投产——第一件商业化的电子乐器」；「与更早的电机械乐器不同，特雷门琴从一开始就设计为完全电子发声」；「1928 年取得专利」；⭐ 「曾向列宁演示，随后巡游欧洲、移居美国」依专题类资料
- ⭐⭐ 「最难演奏准的乐器」：「没有品、没有键、没有任何音挡——每个音高都以连续场的形态存在于右天线周围，没有任何物理反馈告诉你音在哪里」→ ⭐⭐ 名家靠肌肉记忆：「Clara Rockmore（与捷尔明本人共事）为手的位置建立了精确的肌肉记忆；现代演奏者走同一条路——把乐器的空间地图内化」；⭐⭐ 对照全站：牛腿琴把可调件交给手，特雷门琴把整个音高场交给手 —— 手在空中的位置就是指板，而指板看不见
- ⭐⭐ 音色的文化标签：「外星」：「特雷门琴的声音与外星、超现实、怪诞的滑音、颤音相连」；「常被描述为像小提琴，但更诡异、更超凡」；⭐⭐ 电影配乐清单：《爱德华大夫》（Spellbound, 1945）·《失去的周末》·《地球停转之日》（1951）·《火星人玩转地球》·《爱德·伍德》；⭐ BBC Radiophonic Workshop 用它供给世纪中叶的电子声效；⭐⭐ 摇滚：Beach Boys（《Good Vibrations》）· Led Zeppelin · Radiohead
- ⭐⭐ 古典一侧也不缺：「Henry Cowell 与 Edgard Varèse 等古典作曲家为它写过作品」；「肖斯塔科维奇是最早把特雷门琴写进管弦乐的作曲家之一（1931 年电影《Aldna》配乐）」；⭐ 名家：Clara Rockmore 是它最著名的演奏大家
- ⭐ 原型结构：「第一台原型是一只木箱装电子电路 + 一根垂直天线控音高 + 一个踏板控音量；捷尔明很快把踏板换成了水平环形天线——即今天通行的形制」；「1920 年代电路全用真空管；现代设计用运放、模拟乘法器与 CMOS 振荡器 IC——原理完全相同，元件只是更小更稳」依专题类资料
- ⭐⭐ 定位（电子段的起点）：「它是最早的电子乐器之一」与「合成器的先声（a forerunner of the synthesizer）」—— ⭐⭐ 电子段从它写起，因为后面所有合成器的「以电发声、以电压控形」都从这一步开始
- 「特雷门琴属电鸣（Electrophone · 电子振荡发声）」依 Hornbostel–Sachs 分类（1940 年后增补的第五类）
Used for fact-checking only; all prose is original.