Foundations

Most music theory explanations quietly assume five or six things. If any of them has not clicked, everything above collapses into memorisation.

This topic covers those assumptions.

What is actually assumed

That there are only twelve notes. Western music divides the octave into twelve equal steps. Everything else — every scale, every chord, every key — is a selection from those twelve. Pitch and the musical alphabet covers how seven letters cover twelve notes.

That distance is measured in semitones. A semitone is the smallest step; a tone is two of them. Semitones and tones makes that concrete, because scale formulas are written in these units and they are meaningless until the unit is.

That the staff is a grid, not a picture. Vertical position means pitch, and a clef fixes what the positions mean. The staff explains the grid; ledger lines and middle C explains what happens at its edges.

That the same sound can have two names. F♯ and G♭ are one key on a piano and two different notes on paper. Enharmonic notes explains why that is not pedantry.

That notes repeat. Octaves and register covers why a note an octave up is "the same note", and how notes get numbered.

Where to go next

Once these are solid, the natural order is note reading → rhythm → intervals → scales → keys → chords.

Intervals is the hinge. Nearly everything above it is defined in interval terms, which is why skipping it makes scales and chords feel arbitrary.