A measurement of piano playing

Roll width

How widely chords are spread when they are rolled.

What it sounds like

The same passage — Fantaisie-Impromptu, bars 43–46 — from the recordings that sit lowest and highest on this measurement. Every clip is a note list replayed on one sampled grand at one gain, so the only difference you are hearing is the playing.

Least

Murray Perahia, 1985 — bars 43–46, roll width 54 ms15 s

Abbey Simon, 1981 — bars 43–46, roll width 57 ms13 s

Most

Garrick Ohlsson, 1994 — bars 43–46, roll width 153 ms11 s

Nelson Freire, 1983 — bars 43–46, roll width 145 ms11 s

How it is calculated

Last onset minus first onset within a chord written as a block; 90th percentile.

How much pianists differ on it

Every piece in the library, with the range across its recordings. The units mean the same thing in every row, except for basic tempo, which is in each piece’s own beat.

Piece	Recordings	Lowest	Median	Highest
Chopin Étude 10/1	31	16	27	97
Mozart K. 545	37	9	41	78
Rachmaninoff Prelude	29	34	47	76
Gymnopédie 1	23	28	51	132
Pathétique II	47	33	56	238
Ravel Pavane	33	32	61	112
Chopin Étude 10/12	19	25	61	80
Träumerei	31	31	61	182
Schubert Op. 142/3	9	53	66	74
Chopin Ballade 4	12	58	71	97
Nocturne Op. 9/2	32	36	88	162
Brahms Op. 118/2	28	41	90	166
Schubert Op. 90/3	43	47	93	176
Fantaisie-Impromptu	20	54	98	153
Clair de lune	27	46	105	218
Nocturne Op. 48/1	27	81	146	225
Ravel Ondine	61	145	218	275

How reliably it can be measured

A Disklavier capture — the pianist’s own key sensors, no microphone — was rendered to audio, transcribed as if it were a recording, and re-measured. The error the transcription step introduces, as a multiple of how far pianists actually differ on this dial, is 0.39. solid This dial survives transcription intact: where one recording sits on it can be argued from.

All measurements