For fans and indie artists, it’s a democratized music world, and the word is MP3, the downloadable audio format. The evidence? They Might Be Giants, for one, released an MP3-only album, “Long Tall Weekend.” Come here to find the tunes, from artists you know (and those you don’t), along with CD burners, MP3 players, and other digital music paraphernalia. There’s even free MP3 downloads if you want to explore something new, or are just feeling prudent with your cash. So many tunes, you’ll have a lifetime of listening.