A key read into the three things every reader of one needs: the pitch
classes it is built from, the spelled tonic its letter names are anchored on,
and the scale form it stands in.
What a key-shaped argument becomes once it has been read, whatever form the
caller held it in — a name, a scale, a Key. Carrying the tonic beside the
scale is what keeps an A flat minor an A flat minor rather than the G sharp
minor its pitch classes alone would be spelled back as.
A key read into the three things every reader of one needs: the pitch classes it is built from, the spelled tonic its letter names are anchored on, and the scale form it stands in.
What a key-shaped argument becomes once it has been read, whatever form the caller held it in — a name, a scale, a
Key. Carrying the tonic beside the scale is what keeps an A flat minor an A flat minor rather than the G sharp minor its pitch classes alone would be spelled back as.