What "study" means in Pop Boll

The artist agreement says Pop Boll's tiny virtual bands "study" an artist's music. This page says exactly what that means, as the software does it today (9 November 2026). It describes the software. It is not legal advice.

The musicians are rules, not a trained model

• Pop Boll's musicians and judges are rule-based programs built on music theory, seeded random choices and scoring rules. They are not a generative AI model.
• No neural network is trained on anyone's music, anywhere in Pop Boll. There are no weights and no model file in Pop Boll's code, and none on a Pop Boll device.
• Neural networks are used in one place: the offline pipeline that turns a recording into MIDI. It uses four published, pretrained networks as tools: htdemucs to separate the stems, and three for pitch tracking and transcription (a piano transcription network, CREPE and basic-pitch). They run as they were published. None of them is trained or tuned on a corpus, and none of them ships on a device today.

What a corpus gives the musicians

From an artist's MIDI transcriptions, Pop Boll keeps a small "DNA" file for the corpus:

• the shapes of the songs (the order of their parts and how many bars each has), with their tempo and key;
• tempo and key statistics for the whole corpus;
• a handful of one-bar cells per track: a melody, a bass line or a "quirky" melody as the sixteenth-note positions of its notes and their pitches relative to the song's key, and drum patterns as the positions of kick, snare and hi-hat. At most two cells of each kind per track.

What a study break keeps

Now and then a musician takes a "study break" on one track. It reads one random bar and keeps:

• up to 8 note positions of that bar and their pitches relative to the key;
• their loudness shape;
• up to 4 chord names from the track's notes;
• one sentence saying what was studied, plus the track's title, file name and corpus.

These notes are kept in the device's study log, in each song's record (the record of a song lists the study breaks taken while it was made), and with the musician: each musician carries the last 12 cells they studied, and the device keeps a short "hall of fame" of motifs.

Studied cells travel with musicians

When two Pop Boll devices swap musicians over a USB cable, each musician brings their studied cells, and the receiving device adds the last 3 to its hall of fame. So a one-bar cell studied from a MIDI-only artist's transcriptions can end up on another person's Pop Boll, and in songs made there. The recordings never travel. Rare musicians and up never leave their device.

The current decision is that MIDI-only cells may travel, under the licence's "device copies" permission, which every corpus licence turns on by default. If that changes, this page will say so.

Taste does not come from corpora

A song's "taste" (tempo, energy, how strict the tuning is, how much syncopation, which instruments lead) comes from the owner's answers to three taste questions and the colour palette they picked. No corpus is read to make it.

The study guard

Pop Boll is designed so that new songs do not reproduce an artist's parts note for note. While a part is being made, every take is checked against what the device has studied: the cells it holds and every bar of the tracks its musicians studied. A take is turned down when any bar has 7 notes in a row on the same sixteenth-note positions as 7 notes of a studied bar, moving by the same intervals (in any key or octave), and covering at least 4 different notes of the scale. The band then plays another take. If every take is turned down, the best one is kept and the case is logged.

What it catches: a bar, or 7 notes within a bar, of a melody, bass line or riff copied from a studied track, in any key or octave.

What it does not catch: a copy moved off the beat or across a bar line, a copy with a note changed, copies of 6 notes or fewer, plain chord arpeggios, drum patterns, tracks the device has not studied, and likeness in harmony, form or sound. If you hear a Pop Boll song that copies your music, tell us: it is treated as a bug, to be fixed and the song pulled.

What is not built

• Keeping MIDI-only cells from travelling in a USB swap (possible if the decision changes; not built).
• A record of which corpus each travelling cell came from (the track title is kept).
• A check against every track of every corpus at song time (only studied tracks are checked when a song is made; the full check runs in Pop Boll's tests).
• Any check for likeness in harmony, form or sound.
• Automatic tooling to trace a reported song back to the study break that fed it (the song's record has the study notes; acting on a report is done by hand).