The eight columns of a chess board correspond to the eight audible octaves. E.g., C4 is a middle square on the chess board and C4 is “middle C” on the piano…
[The diatonic scale goes from A through G, but a chess board goes up to [del]eleven[/del] H. That’s one higher, innit?]
Fear not! We’ll simply use the Northern European system of musical notation, where an “H” indicates a B Natural, and a “B” indicates a B flat. This is the notation that composers from Schumann to Lizst used to sign the name “B-A-C-H” into their music (see BACH motif).
The remaining task is to assign note values. What makes a quarter note, a half note, and a whole note?
The relative value of chess pieces is Pawn = 1, Knight = 3, Bishop = 3, Rook = 5, Queen = 9, and King = Infinity.
Assigning these exact ratios to note values will create some rather annoying polyrhythms. So let’s round off the ratios a tiny bit and assign the following note values to the chess pieces: Pawn = 1/16th note, Knight = 1/8th note, Bishop = 1/8th note, Rook = 1/4 note, Queen = 1/2 note, and King = rest.
To put the icing on the cake, let’s condense the 8 registers into a single octave to make the chess melodies more tolerable. If a note is doubled (as in 1. e4 e5), let’s jump the second note up an octave to provide some flavor.