Voices

The voices layer counts how many notes sound at once and, on a mono line, reads how each note joins the next. analyze writes it to the voices group of layers.json. It reads any line, chords too, so its fields sit in a group of their own and the pitch group stays null on chords [fact].

Voicing, the chord gate of the transcriber and the pitch layer, does not read this count [fact]. The final notes do: a line with at most one voice at a time, or with no count, is a mono line for every rule of notes.mid and for the span of the full-band level, unless --profile pad ran the notes step (owner decision, 2026-11-05) [fact].

The count

• A note holds a voice from its onset to its note-off knee, or to 25 ms before its end without a knee, so a release tail holds no voice, and a note the envelope layer reads as silent holds none. A held part stops at the stem end, so a note listed past the stem holds none either. A note of 25 ms or less holds none without a knee [fact]. The issue asks for the first note to lie within 3 dB of its sustain level. This reads the knee instead and has no level test [fact].
• Pitches within 60 cents form one voice, so seven detuned copies of one pitch count once [fact, proposal for 60 cents].
• max_polyphony is the most voices that have started by any onset and are held 50 ms after it, so a held overlap under 50 ms does not count [fact, proposal for 50 ms]. mono is true when it is 1, so one overlap of 50 ms or more makes a line poly, with no tolerance [fact].
• mean_polyphony is the mean count over the time any note is held [fact]. An overlap under 50 ms counts here and not in max_polyphony, so the mean can exceed the maximum [fact].
• The confidence is the share of that time whose count agrees with the verdict: one voice on a mono line, two or more otherwise. It reads high from 0.9 and medium from 0.7 [fact, proposal for both].

Joins

Consecutive notes of a mono line join when the later onset lies under 30 ms past the earlier end in the note list, starts after the earlier onset, and lies less than 50 ms inside the earlier held part. A note stacked on another joins nothing and leaves the earlier note in place unless the stacked note ends later, and a silent note leaves it in place too [fact]. gap_ms is negative when they overlap in the list. The split join of the notes step merges a same-key repeat with no attack of its own, so that repeat reaches no join [fact].

• dip_db is the level of the quieter note minus the lowest level from 25 ms before the onset, or from the earlier held end when that comes first, to 25 ms after it, on an RMS over one period of the lower note [fact]. A transcribed onset can land after the silence it follows, which the held end still sees [synthetic]. Each note’s level is the 10th percentile over up to 100 ms beside the join, because that window still ripples on the higher note [fact].
• centroid_change is the centroid over f0 after the join over the same before it, minus 1, over 20 ms or two periods each side, and null when either side holds no signal or runs past either end of the stem [fact]. The verdict does not read it, because it gained nothing on the set below [synthetic].
• legato is true when dip_db is under 1 [fact, proposal for 1 dB]. A 12 dB dip that rises over 5 ms at 110 Hz reads 1.35 dB [synthetic].
• dip_db and legato are null, with no estimate, when neither note has a level above the -120 dB silence floor beside the join, as with notes of about 25 ms or notes listed past the stem [fact].
• A join reads low when its verdict is legato, as a retrigger with an instant attack keeps its level too; when no attack was read; when half a period before the earlier level window or one period before the dip read falls before the stem start; when one period past the 25 ms after the onset falls past the stem end, as a level is then unread or short; or when the median attack of the pool is over 100 ms, because a long attack hides a retrigger [fact, proposal for 100 ms]. Otherwise it reads medium [fact].

The set: 4000 joins sampled over 41 to 440 Hz, steps of -12 to +12 semitones, four timbres, dips of 3 to 60 dB, attacks of 1 to 50 ms, level changes of up to 6 dB, onsets off by up to 20 ms and gaps of -20 to 10 ms, of which 3669 reach a join. At 1 dB, 91 % of the legato joins read legato [synthetic]. Of the retriggers of 12 dB or more [synthetic]:

Limits

• A window of one period of the lower note smears a short new attack, so a retrigger with an attack of 5 ms or less often reads legato, as the table shows. No level read shorter than a period holds still on a periodic wave [fact].

• A retrigger with an instant attack keeps its level, so on generated lines with exact note lists it mostly reads legato: 232 of 270 joins of a retriggered 808, 106 of 127 of a soft retrigger and 81 of 131 of a stepped one, against 150 of 174 of a legato 808. A legato line with a dip reads legato in 46 of 73 joins [synthetic].

• The count reads the note list as it is, so a transcriber’s wrong overlap counts, and one overlap of 50 ms or more makes a line poly. On 889 generated mono lines the chord gate calls monophonic, 136 read poly from transcribed notes, 131 of them at low confidence. With exact note lists, 463 of 463 read mono [synthetic]. On 22 real instrument stems, 1 read mono and none reported a join, at mostly low confidence. The other 21 read a maximum of 3 to 8 and a mean of 1.06 to 2.52 [fact]. So a mapper must not take mono: false or missing joins as evidence at low confidence.

• The verdict depends on where the join falls in the period, and the acceptance test sits on a whole-cycle position. Moving a join from 1.0 s in 0.31 ms steps over 40 positions, between the same saws, read these counts [synthetic]:

  Hz	0 dB join read legato	12 dB, 5 ms retrigger found
  110, 165	31	24
  220, 330	34	40
  110, 146.83	37	24
  82.41, 123.47	29	24

• With under 30 ms of audio after a join, the later note has no level, so a legato join reads as a retrigger: 682 of 960 over four pairs, against 17 of 160 at each length from 40 ms. A 12 dB, 20 ms retrigger reads as one in all but 27 of 960, so the verdict stays and the join reads low, rather than losing those [synthetic]. At the stem start, a join reads low while its earlier level window reaches the start, so up to a lead of about 125 ms. A legato join there reads as a retrigger in 18 to 47 of 160 by lead, from 150 ms on in 27 to 40, and from 1.0 s in 29, so this low level marks a short first note and not a higher error rate. A 12 dB, 20 ms retrigger reads as one in 160 of 160 at every lead [synthetic].

• dip_db reaches 100 to 190 dB on exact digital zeros, since the -200 dB floor stands in for a level. The verdict does not change [synthetic].

• A filter that restarts with no dip in level reads legato. In the set, 228 of 433 filter joins read as a retrigger, against 289 of 436 to 358 of 476 for the other timbres [synthetic].

• A long attack hides a retrigger, and the amplitude envelope may not restart from zero, which makes a dip shallower [fact].

• A pad’s count is a lower bound, because pads are the weakest class of the transcriber [fact].

• Glides and legato inside chords have no method here [fact].