BEEP BOOP
Journal 12

Every note in key

On SYNTH, every tune you draw sounds right. That is not a filter on wrong notes. The grid has no wrong notes to play: its eight rows are the eight notes of one scale, and nothing else.

Fig. 1
SYNTH's eight rows, from the foot up: row 1, C, 0 semitones above C, 261.6 hertz; row 2, E flat, 3 semitones above C, 311.1 hertz; row 3, F, 5 semitones above C, 349.2 hertz; row 4, G, 7 semitones above C, 392.0 hertz; row 5, B flat, 10 semitones above C, 466.2 hertz; row 6, C, 12 semitones above C, 523.3 hertz; row 7, E flat, 15 semitones above C, 622.3 hertz; row 8, F, 17 semitones above C, 698.5 hertz. Of the 18 semitones from C to the F an octave and a half above, these eight are the only ones the grid can play.CE♭FGB♭CE♭FIN KEYC4ROW 1 · +0 · 261.6 HZE♭4ROW 2 · +3 · 311.1 HZF4ROW 3 · +5 · 349.2 HZG4ROW 4 · +7 · 392.0 HZB♭4ROW 5 · +10 · 466.2 HZC5ROW 6 · +12 · 523.3 HZE♭5ROW 7 · +15 · 622.3 HZF5ROW 8 · +17 · 698.5 HZ
C minor pentatonic on eight rows. The top line is every semitone from C up to the top row's F; the orange ones are the only notes the grid can play. Pitches are for a sound at octave 0; each sound and OCTAVE move the whole grid by octaves.

Rows, not keys

A piano has twelve notes to an octave, and most tunes use seven or fewer of them. A beginner's wrong note is almost always one of the other five. SYNTH leaves them out. Its grid is eight rows of steps, and each row is a note of C minor pentatonic, engraved beside it: C, E♭, F, G, B♭, then C, E♭ and F again an octave up.

A pentatonic scale has five notes, no two of them a semitone apart. With no semitone in it there is no clash to find: any two notes of the eight played together, or one after the other, sit well. That is why a tune drawn at random on the grid still sounds like a tune.

The rule

Each row is a number of semitones above C: 0, 3, 5, 7, 10, 12, 15 and 17. The engine adds that to middle C, which is note 60, and to twelve for each octave the sound and OCTAVE are set to. The pitch is then 440 hertz times two to the power of the note, less 69, over twelve. That is the whole of it, worked out as each note starts.

A seven-note scale would end at its octave on the eighth row. The pentatonic keeps climbing past it, so the eight rows reach an octave and a half, from C to the F above the next C. Fig. 1 shows the eighteen semitones in that span, and the eight the rows can play.

One key, chosen once

In this version the key is C minor pentatonic for every tune, and the player does not choose it. The engine can hold any of twelve keys and five scales: minor and major pentatonic, minor, major and dorian. A printed tune carries its key in its code. Today every one is written in C.

One key for everything is the point as much as a limit. A beat and a tune made on the same phone always fit together, and so does any tune scanned from a friend's receipt.

PADS, in the same key

PADS has a key called SPREAD. It lays one sound across all twelve pads in SYNTH's key, so whatever pattern your fingers make on the pads is a melody too.

Sources

More sheets

  1. How Beep Boop makes a soundTwo voices, TEAR, and one path out.
  2. An instrument in SwiftUIOne accent, a key lit from inside, nothing unneeded.
  3. A kick drum is twelve numbersHow a drum machine's kit is built.
  4. The audio thread never waitsNo allocation, no lock, one queue.
  5. PatternsDrum patterns drawn on sixteen steps.
  6. Tempo by genreBPM for twelve genres, on one scale.