Re: Jon "Bermuda" Schwartz here!
Al's originals (which account for 50% or more of the material on each album) each have a specific style, and are often a homage to some of Al's favorite artists (DEVO, Zappa, Aerosmith, Talking Heads, Boingo & MANY many more...) So from the start, we know the feel he wants, and the kind of signature parts and sounds that will help convey that. Sometimes we are left to our own devices, and sometimes Al wants a very specific part or fill. So there's a certain amount of input that we have on the originals, and over the years we've learned there are certain little things he likes, so we don't require a lot of direction. But as the writer/artist/producer, Al always has the final word.
The process is also very efficient: Al makes a demo for us with 5 or 6 originals, we think about parts for a few weeks then get together once to rehearse and massage the parts. Then the band records a demo and we privately ponder the songs a little more and zero-in on parts. Then we're in the studio, ready to cut them all, usually in one day.
With the parodies, there's no input whatsoever, since we're copying existing parts & sounds. If Al says we're doing "Pretty Fly For A White Guy" (Offspring,) we use that recording as a road map, possiblly incorporating arrangement or key changes. We do a huge amount of pre-production on our own in terms of writing-out parts, assessing sounds, and in the case of sequenced songs, creating samples and sequences. No rehearsal is necessary, since there are no subjective parts to work on - we are copying another song note-for-note - and we show up at the studio playing the songs for the first time as a band, typically tracking them all the same day.
With respect to the parodies, copying parts and sounds is difficult work. We aren't permitted to just 'get the flavor' or play a few signature parts. Our version has to be as close as possible to 100% accurate, with the knowledge that 99% is probably not acceptable. It's often a trying process where we have to 'backwards engineer' recordings to decipher parts and how sounds were achieved. I'm pretty sure that there are no other guitarists, bassists, or drummers who have the sense of purpose (or the patience!) to chart every note, every dynamic, every mistake, and every tempo change for their recordings.