Dear Editor, I've been reading a lot lately about the analytical forms of rock music, one guy even going so far as to mention Mingus and so on ["Postmarks," Jan. 2]. First of all Mingus played jazz. Jazz musicians play fast all the time; they know all the notes, when to play this, when to play that. All of this having nothing to do with rock. Rock was built on simplicity. Whether you can play three chords or 19, fast or slow doesn't matter. Anybody who says this band is better than that band is missing the point. Rock is about power, rhythm, sadness, love, and feelings I can't even write down on this paper. Not only that, all rock is corporate, if you sell albums, if people pay you to play, you're corporate! Just as Chuck Berry, who hoarded money and paid stand-ins because he was too cheap to keep a real band. And for all you punk rockers, I'd just like to say, as I fire up a joint and slap on some Zeppelin, rock on.