Circuits is a wonderful puzzle game to challenge your musical hearing abilities... ...if you don't already have over a decade of musical experience.
99% of you are probably don't have the best ears in the world when it comes to music, so for most of you out there, I will definitely recommend this. But be prepared for some pretty difficult puzzles!
However, for those with a history of extensive musical training, don't expect to use much thought process. I myself am a music composition major in university, and have been playing music since the age of 2. Needless to say, I was able to complete all the puzzles with total ease, without using any hints or switching to individual instrument layers. If you think you would be in a similar position as me, either wait until more difficult puzzles are introduced into the game (the devs are considering adding some more challenging levels), or simply get the game now, and use it as a method to relax.
On a side note, I hear there is a new extention or software coming soon called Circuits Composer, which means that the community might be able to provide us with some truly challenging puzzles, possibly even for music graduates.
My final word is that I fully recommend this game to people who don't have impossibly sharp ears, as you'll be developing your hearing abilities through levels that you may find yourself stuck on for hours. And even for the others, I would still recommend the game, given that you keep in mind my comments above.
I'll be looking forward to any future updates!