I bought these for two purposes: Playing digital piano and for tracking vocals and guitar. For both purposes these do very well. They are comfortable to wear, although they can feel a bit warm and clammy if you are wearing them for hours at a time. They are very isolating, shutting out external sounds as good as hearing protectors - you could probably use them when playing/recording drums. The sound leakage to the surroundings is also very good, and when recording vocals while wearing these I can detect no sound getting picked by my condenser microphone.
The sound is very clear and open. Compared to my other headphones from Sennheiser, Klipsch and Koss, these are lacking a bit of bass, not really delivering that deep punch despite being marketed as more bass-heavy. The comparison is a bit unfair though, as the other headphones all cost between 5 and 10 times as much. For the price you pay for these, they are absolutely marvelous. They are hands-down the best sounding headphones in that price range I have ever used. Sure, others I have tried may have had better deeper bass response, but they are nowhere near the clarity and brilliance of these.
When my spouse was playing the digital piano using her old headphones, I asked her to try these on. She played for only a few seconds, then turned to me and said upset: "Damn you, you've ruined my old headphones!". She is now always borrowing these from me, refusing to go back to those she was happy with before trying these on.
