band practice 7.18.26 · perf09 · bass written to order
Two bass lines for the same guitar take. The first one agrees with the guitar. The second one keeps changing what the guitar means.
Everything below is read from MIDI guitar.mid, MIDI kick.mid,
MIDI snare [2026-07-23 174311].mid and MIDI cymbals [2026-07-23 174806].mid,
the stem transcriptions of the perf09 take. Bar numbers come from the beat grid tracked across those
drum files, so bar 1 begins at tick 125 and bar 53 at tick 17839.
The guitar take is a transcription of a live performance, so it carries no usable grid of its own. Measured over the whole 94 seconds, the best constant pulse scored a normalised grid error of 0.196 against 0.25 for random. There is no fixed tempo in that file to quantise to.
Weighted by how long each note sounds, the part is G 38%, F♯ 21%, B 18%, E 12%, and every low note in it is an open E2. That is an E minor figure sitting on an E pedal. The top line barely moves. Bars 47 through 50 are one unchanging G4 repeated across four bars.
Agrees with the guitar. E under the E sections, B under the F♯/B sections, G under the low G passage. It supports the part and stays out of the way.
107 notes. The guitar's G reads 2 ways across the whole piece.
Same guitar, same drums. The bass walks i → ♭VI → IV → V underneath, so a guitar note that never moves keeps arriving in a new chord.
131 notes. The guitar's G reads 5 ways.
Real guitar and real drums from the perf09 stems. The bass is synthesised from the MIDI.
Bars 47 to 50, highlighted in the table below, are one G4 held over and over. v1 calls it the flat third of E minor four times. v2 moves the floor and the same note becomes the flat third, then the fifth, then the flat seventh, then the flat sixth. The guitarist plays nothing new.
Guitar column lists the three longest-sounding notes in that bar, measured by sounding duration
inside the bar window from MIDI guitar.mid. Shaded interval chips are the colour tones,
meaning the note falls outside the plain triad underneath it. Bars 7 to 13 are absent because the
guitar plays nothing there.
| bar | guitar | v1 | reads as | v2 | reads as |
|---|---|---|---|---|---|
| 1 | G4 B3 | Em | G b3 B 5 | Emi | G b3 B 5 |
| 2 | G4 | Em | G b3 | Emi | G b3 |
| 3 | B3 G4 E3 | Em | B 5 G b3 E root | C♭VI | B maj7 G 5 E 3 |
| 4 | B3 E2 E3 | Em | B 5 E root E root | Emi | B 5 E root E root |
| 5 | B3 | Em | B 5 | C♭VI | B maj7 |
| 6 | B3 | B | B root | BV | B root |
| 15 | G4 | Em | G b3 | C♭VI | G 5 |
| 16 | G4 F#4 | Em | G b3 F# 9 | AIV | G b7 F# 13 |
| 17 | E2 F#4 | Em | E root F# 9 | Emi | E root F# 9 |
| 18 | B3 E2 F#4 | B | B root E 11 F# 5 | BV | B root E 11 F# 5 |
| 19 | F#4 F#5 | B | F# 5 F# 5 | D♭VII | F# 3 F# 3 |
| 20 | F#4 E2 | Em | F# 9 E root | Emi | F# 9 E root |
| 21 | G4 B3 F#5 | Em | G b3 B 5 F# 9 | Emi | G b3 B 5 F# 9 |
| 22 | G4 | Em | G b3 | C♭VI | G 5 |
| 23 | G4 | Em | G b3 | AIV | G b7 |
| 24 | G4 E2 F#4 | Em | G b3 E root F# 9 | BV | G b6 E 11 F# 5 |
| 25 | F#4 B3 | B | F# 5 B root | Emi | F# 9 B 5 |
| 26 | F#4 B3 | B | F# 5 B root | C♭VI | F# #11 B maj7 |
| 27 | F#4 E2 B3 | B | F# 5 E 11 B root | BV | F# 5 E 11 B root |
| 28 | B3 | Em | B 5 | Emi | B 5 |
| 29 | B3 E2 E3 | Em | B 5 E root E root | Emi | B 5 E root E root |
| 30 | E2 C#4 F3 | Em | E root C# 13 F b9 | D♭VII | E 9 C# maj7 F b3 |
| 31 | E3 F#3 | Em | E root F# 9 | C♭VI | E 3 F# #11 |
| 32 | F#3 E3 | B | F# 5 E 11 | BV | F# 5 E 11 |
| 33 | E3 E2 F#3 | Em | E root E root F# 9 | Emi | E root E root F# 9 |
| 34 | F#3 | B | F# 5 | D♭VII | F# 3 |
| 35 | E2 G3 G#3 | Em | E root G b3 G# 3 | AIV | E 5 G b7 G# maj7 |
| 36 | G3 D3 | G | G root D 5 | G♭III | G root D 5 |
| 37 | F#3 C#5 G3 | G | F# maj7 C# #11 G root | AIV | F# 13 C# 3 G b7 |
| 38 | G3 G4 | Em | G b3 G b3 | Emi | G b3 G b3 |
| 39 | G4 B3 | Em | G b3 B 5 | Emi | G b3 B 5 |
| 40 | G4 | Em | G b3 | C♭VI | G 5 |
| 41 | G4 | Em | G b3 | AIV | G b7 |
| 42 | G4 | Em | G b3 | BV | G b6 |
| 43 | E2 B3 G4 | Em | E root B 5 G b3 | Emi | E root B 5 G b3 |
| 44 | F#4 B3 E2 | B | F# 5 B root E 11 | BV | F# 5 B root E 11 |
| 45 | F#4 E2 B3 | B | F# 5 E 11 B root | C♭VI | F# #11 E 3 B maj7 |
| 46 | F#4 A#3 B3 | B | F# 5 A# maj7 B root | D♭VII | F# 3 A# b6 B 13 |
| 47 | G4 B3 E2 | Em | G b3 B 5 E root | Emi | G b3 B 5 E root |
| 48 | G4 | Em | G b3 | C♭VI | G 5 |
| 49 | G4 | Em | G b3 | AIV | G b7 |
| 50 | G4 | Em | G b3 | BV | G b6 |
| 51 | G4 E2 B3 | Em | G b3 E root B 5 | Emi | G b3 E root B 5 |
| 52 | F#4 B3 E2 | Em | F# 9 B 5 E root | Emi | F# 9 B 5 E root |
| 53 | F#4 B3 | Em | F# 9 B 5 | Emi | F# 9 B 5 |
The bass is locked to attacks rather than to a grid, because the grid drifts. A dynamic beat
tracker run over the onsets in MIDI kick.mid, MIDI snare [2026-07-23 174311].mid
and MIDI cymbals [2026-07-23 174806].mid returned 212 beats at a median 85.0 ticks,
which is 135.5 BPM, drifting between 132 and 137 across the take. Quantising to any single
tempo would have walked the bass out of the band by the end.
Every attack coincides with something the band actually played. The placement pool is the kick, the snare, the cymbals and the guitar's own onsets, merged so that hits within 12 ticks count as one moment, and ranked so the kick wins. 96% of the 131 notes fall on a drum hit, and every remaining note falls on a guitar attack. Nothing is placed on the tracked grid.
The tracked beat is used to decide where the bars are, never to place a note. It interpolates a steady pulse straight through the passages where the band stops, so a note put there would be playing to a click nobody else can hear. Bar 14 gets no bass at all for that reason: the nearest attack of any kind is 244 ticks away.
The first version placed notes on that interpolated grid whenever the drummer left a gap, which is what read as off. Measured against the take:
| check | first pass | now |
|---|---|---|
| notes falling on a real drum hit | 63% | 96% |
| notes coinciding with nothing at all | 21 of 135 | 0 |
| pairs tighter than an eighth note | 9 | 0 |
| smallest gap between attacks | 32 ticks | 52 ticks |
| downbeats floating in a drum rest | 11 | 0 |
| worst root offset from its bar line | 245 ticks | 44 ticks |
MIDI bass v2.mid the moving floor, 131 notesMIDI bass v1.mid the root bass, 107 notesperf09 tempo map.mid the tracked 135.5 BPM map, optionalpreview v2 (band + bass).wav and the v1 twin, 24 bitAll of it in ~/Projects/_outputs/midi-bass-perf09/