Sorry for the confusion here -- you're not the first to ask, but the TLDR is that you can't (right now)!
We do hope to allow octave selection in a future "practice" mode where you're not limited to one puzzle a day, though.
The reason you can't right now is because it gets a little complicated if the user selects the right note but the wrong octave; they'll hear the correct pitch when they play the note, but should we record the wrong octave in the playback, or play the right octave (but potentially cause confusion, because it wasn't exactly the note the user selected?) The easiest thing to do seemed to select the octave for the user, but I'm open to feedback on how to make this less confusing with the maximum fun.
We do hope to allow octave selection in a future "practice" mode where you're not limited to one puzzle a day, though.
The reason you can't right now is because it gets a little complicated if the user selects the right note but the wrong octave; they'll hear the correct pitch when they play the note, but should we record the wrong octave in the playback, or play the right octave (but potentially cause confusion, because it wasn't exactly the note the user selected?) The easiest thing to do seemed to select the octave for the user, but I'm open to feedback on how to make this less confusing with the maximum fun.