Slide the shape, keep the tune

A melody is a shape

Here is the opening of Ode to Joy as a contour — a connected shape laid over the keys. Transposition is nothing more than sliding that shape: pick a shift and play. Every interval inside the melody survives the move, which is why it stays recognisably the same tune from any starting note.

What to try

0, then +2, then +7. The shape never bends — only its altitude changes. If you can hum it at one position, you can hum it at all of them; your memory stores the shape, not the notes.

Watch the black keys appear. At some shifts the rigid shape is forced onto black keys — the same forcing that gives transposed music a new key signature.