The Improviser · Lesson 1 — Note by Note

Note by note — tokens.

A model doesn't take in a whole melody at once — it reads a stream of small pieces called tokens.

A musician reading sheet music doesn't swallow the tune whole. They take it in one event at a time — this note, that duration, the next note — and it's the sequence of those small events that makes a line. Nothing arrives as "the melody"; it arrives as a run of little symbols on the page.

An LLM reads much the same way. Before it can do anything, it first cuts the input into tokens — small pieces. A single plain note is one token; something richer, like a chord, splits into several. The model only ever sees this stream of tokens — never "the tune" itself. And each token reaches it as a plain ID number, which is all the numbers on the right are.

Take a short phrase and break it into tokens yourself — hear each one land — then see the raw numbers the model actually reads.

A phrase is just a run of events. Break it into tokens.
C · D · E · G · [ C-major chord ]

The same phrase, as the model takes it in.

You hand over the notes; the model first splits them into tokens. A single note is one token — but a chord stacks into several, one per pitch.

tokens = model.tokenize(["C", "D", "E", "G", "Cmaj"])
# → ['C', 'D', 'E', 'G', 'C', 'E', 'G']

len(tokens)     # 7 tokens
tokens[4:7]    # ['C', 'E', 'G'] — one chord, three tokens

Everything is tokens.

The phrase, the answer, every note the model reads or plays — all of it is a sequence of tokens. The model never sees a staff or a feeling directly; it sees these small pieces, and the numbers behind them.

Tokens are the unit an LLM works in. Where the odds over the next token come from — how the model learned to guess it at all — is the next page.

Quick check · your ear
The phrase looked like 5 events, but tokenized to 7. Why the extra two?
Next: the practice room →
You've just heard the soloist choose three notes. That's the whole trick.
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