Well, I love both restraint and jamming. I hate to keep making an example of Floyd, but there was a time where I had wished they'd jam here and there live. Then came a point where I realized it'd have a complete different impact and disrupt the atmosphere of the music and show. With other bands, I feel that jamming is beautiful, and restraint would destroy them. Take RHCP. I think John Frusciante and Flea have excellent chemistry as the two string/melodic instrumentalists of the groups, and the four-way connection of the band is even more impressive. If they didn't utilize that connection by almost telepathically going into jams and improvisations at their live shows, I think it'd be a waste of a gifted relationship.

Then you have post-rock, as I've mentioned. Post-rock songs, Dependant on band, seem to range from 6-30 minutes, and yet I think they still have a restraint. Jamming would ruin that restraint, and cutting the songs down to four minutes would also ruin that restraint, if you can make sense of that... It's a rather minimalistic genre, I think the restraint comes from not fighting to do too much, but still managing to make an impressive wall of sound with conventional rock instruments like guitar, bass, drums, and occasionally keys, and then still working in complimentary instrumental cells like string quartets, brass bands, electronic sampling and experimentation, and so on.