It depends, if someone, say the guitar player comes in with a whole song done and the band goes with it like that then he gets the credit, if you guys are jamming and start the writing process from there, the whole band gets credit, If you come up with a riff and bring it to the table and the bass player comes up with another part and you 2 finish it, Hey the variables are infinite. I myself write a whole song, take the best riff(s) from that song and bring it to the table, I have written a whole song and tuaght everyone how to play it, but I find that as our band has Three guitarists, if one person writes an entire song than it deosn't really sound like the rest of the material you have, after all it is called a BAND for a reason. I also arrange and the other guys depend on me to tell them what to use and what not to and how many times and in what order, that is what arrangers do, also I write some of the lyrics, usually our vox man does but sometimes I get the urge. I don't use material that is not absolutely 100% my best, doing this may take a little longer to write, but the product is 100% better. If I write a song and there is a weak riff, I replace it with a better one with more flow, I do this when the guys come in with a song too, but when they here the riff I have for their song or they here a riff put into another song they don't complain. I guess I got a little off subject, our band gives credit to the whole band, also I feel that drums can change the whole feeling of a song from what you originally intended, therefore I think drummers deserve more credit than they get.