Missing Notes

A run of notes with one of them missing. On a staff, in treble, bass, alto or tenor clef, that's a run of five; on a piano keyboard it's a full octave of eight white keys with four of them left blank. You press the gap, then name the letter that belongs there.

On the keyboard, pointing at the gap first is the whole point: the blank key sits among labelled neighbors, so you read where it falls before you can say what it's called. On the staff the gap is the only blank position, so there's nothing to locate — naming it is the whole exercise.

Staff view alone carries a settings gear with the run controls: ascending, descending and skips/leaps are independent switches that combine rather than exclude each other — turning skips on adds bigger steps to the pool instead of replacing stepwise motion — plus ledger lines, which let the run reach past the staff.

Nothing here is saved and no account is needed. Get it wrong twenty times and nothing is written down anywhere.