> If the environment is noisy and headphones are necessary, music without lyrics. I tend to like trance or orchestral movie and game soundtracks.

I'll take this opportunity to plug my ambient noise generator:

http://asoftmurmur.com

There are other non-music options too:

http://coffitivity.com

http://noisli.com

http://rainycafe.com

http://mynoise.net <- very customizable. Great for enthusiasts