skills/ensemble-arranging/references/string-quartet.md

# String quartet

## Roles

| Part | Default role | Alternatives |
| --- | --- | --- |
| violin ("Violin 1") | melody | unison with violin 2 for weight |
| violin ("Violin 2") | harmony a third or sixth below, or counter-melody | repeated-eighth accompaniment with viola |
| viola | inner voice, rhythmic figure, or countermelody | melody for a darker phrase |
| cello | bass line, roots and fifths | melody in the tenor register (A3 to A4) with viola taking the bass |

## Textures (change every four bars, not every bar)

- **Chorale**: all four in the melody's rhythm, complete triads, cello on
  roots.
- **Melody with accompaniment**: violin 1 melody, violin 2 and viola in
  repeated eighths on chord tones (broken or together), cello quarters on
  roots and fifths.
- **Imitation**: violin 1 states the motif, viola or cello repeats it one or
  two bars later a fifth or an octave away while violin 1 holds.
- **Unison or octaves**: all four on the melody for one phrase, for emphasis.
- **Pedal**: cello holds an open string (C2, G2, D3, A3) while the upper
  three move.

## Part-writing rules (common-practice)

- Complete triads on strong beats; when a voice must be omitted, drop the
  5th. Double the root, in a first-inversion chord the soprano or bass.
- Spacing: violin 1 to violin 2 and violin 2 to viola within an octave.
  Viola to cello may exceed an octave.
- No voice crossing and no overlap (a lower voice moving above where the
  upper voice just was).
- Inner voices move by step or hold common tones. Melody and bass prefer
  contrary motion.
- No parallel perfect fifths or octaves between any two parts. Parallel
  thirds and sixths are the sound of the quartet.
- Leading tone rises to the tonic; chordal 7ths fall by step; a 4-3
  suspension resolves down on the next beat.
- Cadences: V to I with the cello moving by fifth; a half cadence ends a
  four-bar phrase on V; the melody ends a phrase on the 3rd or 5th, the
  final one on the root.
- Chord changes on strong beats; harmonic rhythm of one or two chords per
  bar. Use the beat `chord` field for the second chord.

## Registers and idiom

- Cello below C3 alone; viola C3 to C5; violin 2 G3 to E5; violin 1 D4 to E6
  for melody, higher only for a peak.
- Fast passages stay on adjacent strings; a leap across strings needs a
  longer note first.
- Double stops on adjacent strings in thirds, sixths and octaves, held or
  in quarters, never in fast sixteenths.
- Not all four instruments change notes on the same beat for a whole
  phrase; hold at least one voice through each bar.
- Give one instrument a bar of rest every four to eight bars.