I meant to play and I found it a bit harder than the rest compared to the other instruments on each level, not only on level 1. Level 3 I did find that the difficulty went up by a bunch, but seeing that it's only the three levels for now, I think it's very much okay. I would put a level or two when adding the new ones between the actual Level 2 and Level 3 that exist right now, or tone the Level 3 difficulty down a bit (haha get it? tone down? sorry).
Also, about the bass, just a bit louder should be fine (or its frequencies enhanced and the other instruments lowered on those freqs when the bass appears). My speakers are usually okay with low frequencies and I could hear it, but it just got overridden by any other instrument very easily.