I was voting for the importance of the instrument when it does feature in the band and how much it being played well or badly affects the music. Thus I voted for drums, as good drumming really gets a song going, whereas bad drumming tends to ruin it.

Big Bottom, by Spinal Tap, doesn't have a (non-bass) guitar in it, Don. Although they ARE a spoof band...

Oh yes, ol' Spiney.

Hmm, I dunno about your logic, couldn't you say the same for all the instruments?

Yes. This is one of those IMO moments. The logic for this one stops at your own preference. Badly played drums (particularly badly timed ones) tend to throw all of the other instruments out more noticeably than badly played guitars, keys or vocals. Other instruments do mess up other parts of the song if played badly, of course.

ELP qualify as rock, and many of their songs have no guitar...Béla Fleck & The Fleckstones are also a guitarless band with a very rockin' feel.

Radioheads National Anthem is also a pretty rockin' song and it has no guitar, at least that i know of.

And then of course there was Jerry Lew Lewis who could write a great rock n roll song for just piano, bass and drums.

The bass pure an simply because of Dos.

dos?

Dos is a bass duo of Mike Watt (Minutemen) and Kira (Black Flag).

Drums are definently the most important becasue without a good steady beat to keep tempo, your band is hopeless

...unless your band doesn't have drums.

I think drums, bass and guitar are all equally important to a song's structure. If one is missing, the song is lacking a very important ingredient!