It can be a bit difficult to find notes quickly on the instrument interface currently, as there are no accents marking notes as a piano might have (e.g. the wedge on the C, E, F & B keys at every octave).
I can think of a couple of ways this could be improved, making it much more convenient to play pieces with the instruments in hand:

• Have slight variations on the borders and colours around each note (e.g. a lighter hue on the natural keys and a darker tone on the sharp/flat keys, and alternating between grey & white on the note highlights)
• Shorten the visible length of sharp/flat keys (but still allow clicking on them from the full length)
• Show a different segment above the C key of each octave, helping it stand out from the rest of the notes
• Add wedges at the bottom of each key, similar to those found on a piano

I understand a lot of it may come down to practice, but it would be nice to see some or all of these changes implemented to help make the experience more intuitive and enjoyable.