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PitchRegisterTimbreChinese Pentatonic ModesGuqinPipaDiziBianzhongViolin

The erhu is the melodic mainstay of the Chinese orchestra and the instrument most often said to sound "closest to the human voice". But its real character lies not in its timbre but in two extremely unusual design choices:

⚠️ First: the bow cannot be taken out. The erhu's bow is not a separate tool — the hair runs between the two strings. The stick is above, the hair below, and the two strings sit in the gap between them. A whole chain of consequences follows, none of which Western strings have: it cannot "tap with the bow and put it back", and it cannot let both strings rest in silence. The bow is permanently inside the instrument, so bowing is its only principal means of sound. In exchange it gains something a violin cannot do: crossing from the inner string to the outer one is almost instantaneous — because both strings sit on either side of the same hank of hair.

Structure: one hank of hair between two strings

Three points:

1. The hair sits between the strings. This is the essential difference from the violin: a violinist can lift the bow, tap with it, or take it right away. The erhu's bow is threaded into the instrument. So it has almost no silent state, and its music is continuous by nature. 2. The body is headed with python skin. Note that this does not make it a membranophone — the test is still what vibrates: the strings vibrate, and the skin is a resonator. It gives the erhu that slightly nasal, voice-like colour, and makes it sensitive to weather, since the skin tightens and slackens with humidity and temperature. 3. No fingerboard, no frets. The fingers press on strings suspended in air, so pitch is a continuous line and slides become the instrument's core language — the same geometry as the guqin, but plucked versus rubbed.

Two strings, three octaves

That is how two strings produce three octaves: the two bands are offset by a perfect fifth and overlap, so together they cover D4 to A6.

"Shifting position" therefore becomes one of the erhu's core techniques: the left hand does not merely press, it travels bodily along the neck. And that has an acoustic consequence: there are seams between positions, so notes that cross a position must be joined by a slide — which is how the slide turned from an ornament into the erhu's grammar.

*(The historical comparison is startling: before Liu Tianhua's reforms the erhu's range was only a ninth, with a single position — it could not even play a moderately complex melody.)*

Range

二胡属弦鸣乐器（擦弦，无品无指板）。内弦空弦 D4、外弦空弦 A4（相隔纯五度）。刘天华改革之前音域只有九度、只有一个把位；把位增至五个后，有效音域扩展到三个八度左右，分低 · 中 · 高 · 最高四个音区。本图取常用音域 D4–A6。千斤至琴码的距离通常固定在 46–48 厘米。记谱即实音。

• Inner string D4, outer A4 (a perfect fifth apart) — the standard Liu Tianhua fixed, and the precondition for the erhu joining an ensemble: without a standard pitch there is no playing together.
• Working register D4–D5: the first and second positions, where most melodies live.
• Before and after the reforms it is two different instruments: a ninth → three octaves, positions one → five. That is not a question of craftsmanship but of turning a folk accompaniment instrument into a solo instrument.

Timbre, and how to hear it

Four cues:

1. The most voice-like Chinese instrument. Focused upper-middle register with a slight nasality — which is why it is often used to "sing" (*Reflection of the Moon on Erquan* is a sigh turned into sound). 2. A continuous line. With the bow permanently in the instrument there is almost no real interruption; phrases are marked by the breath of the bow and by slides. 3. Slides are grammar, not ornament. The seams between positions plus fretless continuous pitch make the slide the erhu's signature. 4. Its sound changes with the weather. Skin tightness follows humidity and temperature — a daily reality for players.

Playing techniques

• The right hand bows. Because the bow cannot be removed, crossing strings is nearly instantaneous, while techniques that take the bow off the string — staccato, spiccato — have to be worked around.
• The left hand stops and shifts. No fingerboard means continuous pitch; shifting means seams between positions, bridged by slides.
• Vibrato. Liu Tianhua imported the violin's vibrato — a leap in the erhu's expressiveness.
• Pizzicato exists but cannot replace the bow; with the bow inside the strings it can only be a colour.
• The two strings are two colours. Inner is thick, outer is bright — the same melody sounds different on each, a device erhu writing uses constantly.

The family

The same objects, two maps: in the bayin this whole family is silk (strings), while in HS "plucked" and "rubbed" are different classes. The bayin does not distinguish how the string is set in motion; HS does — the most visible difference between the two systems.

History

The one thing to remember: within thirty years the same instrument went from "street accompaniment" to "solo instrument" — and the change began not with materials or craft but with one man giving it a pitch, positions and repertoire.

Common misconceptions

• "Its bow is like a violin's." Not so: the erhu's bow cannot be removed — the hair runs between the two strings, while a violin bow can leave at any moment.
• "Its skin head makes it a membranophone." No. The test is what vibrates: the strings (chordophone); the python skin is a resonator.
• "Two strings must mean a narrow range." A modern erhu covers three octaves (D4–A6 in practice) — through shifting position, not string count. The range ceiling is set by where the hand can travel, not by how many strings there are.
• "It only plays sad music." Its most famous work is indeed bleak (*Erquan*), but *Horse Racing* and *March of Light* are equally central to its repertoire.
• "It has always been a solo instrument." Before Liu Tianhua it was mainly an accompanist for opera and narrative song; its solo identity dates from the 1920s.
• "The bayin says silk, so steel strings are wrong." The same point as with the guqin: the bayin describes the material of its own time, and the name is inherited.

Next

The silk category is not finished: the pipa is also "silk", but it has frets — and that turns pitch from a continuous line back into steps. One string, with or without frets, is two different instruments. And once we cross from silk to bamboo, the dizi changes the whole discussion: no strings at all, only the air inside a bamboo tube. :::

Sources

• 形制依通行乐器资料：琴筒（一端蒙蟒皮）· 琴杆 · 两根弦 · 千斤 · 琴码 · 竹弓（张马尾，夹于两弦之间拉奏）；无指板 · 无品
• 「二胡属弦鸣乐器」依 Hornbostel–Sachs 分类 —— 振动体是弦；蟒皮是共鸣体，不是发声体
• 「普遍采用五度定弦，通常内弦定 d1、外弦定 a1」依通行资料 —— 即 D4 · A4
• 「改革前音域只有九度；把位增至五个后，有效音域扩展到三个八度左右，分低 · 中 · 高 · 最高四个音区」依刘天华改革记述
• 「琴筒由圆形改为六角形；千斤至琴码的距离基本固定在 46–48 厘米；内弦定 D、外弦定 A」依刘天华改革记述
• 「华彦钧（阿炳，1893—1950）与刘天华（1895—1932）对二胡演奏艺术作出创造性贡献」依乐器史
• 「二胡属于八音中的丝（传统用丝弦，今用钢丝弦）」依通行资料

Used for fact-checking only; all prose is original.