This is a tough one, but here are a few tips I learned from our last cd. A sound technician will certainly have a better handle on this, but here goes.

If you are playing it through a poor system (computer, small box), the sound quality is very limited by the speaker quality, which is generally poor. That means it will sound better, in a way, because the bad things won't be as obvious, everything sort of get levelled out. On the other hand, it might also sound really tinny or you might lose certain frequencies (the whistle?).

If you listen on an excellent system (studio) you will hear a more true representation of the sound. However, hardly any one else is ever going to play it in a studio type system.   Head phones on a nice system is a good starting place. Beyond the levels, listen to see if you get separation of the sound. For most types of music, there should be a sense that the instruments are placed in the room (front to back, side to side). Listen for tone in the instruments (this can be majorly tweeked in the mastering process). Then you can take it to your car and computer, note the discrepancies and ask your mastering guy about what your hearing and why.

Good luck, and I would be very interested to hear what you and others say about this. My band is going for another one in the spring, so it is already on my mind.

Claire