Knobswitch

It is easiest to do this in Level 1. At the start of each round, without pressing or to listen to the two notes, select “Octave” for the answer. Since there are only three available answers this level, you have a 33.33% chance of it being correct. If it’s not, listen to the notes and select the right answer, then rinse and repeat with the second round. It is 98% guaranteed you will get at least one pair of notes with an Octave interval in the first round of Level 1.

Once you have guessed correctly without listening to the notes, the trophy will unlock.