I've had the opposite experience as well. Back when I was at Berklee in the early 80s and collaborated with some New England Conservatory folks all the way up to the more recent past, I've had wonderful improvisations with people from a classical background. I've discovered that those that are open to it are much more willing to suspend all preconceived notions of musical style and put their full attention and intention into listening and creating a language of the moment. This can come from completely free improv to using non-traditional materials as scores.
In contrast, with many rock musicians improv seems to mean rehashing blues rock licks without much attention to what's going on around them. I've had similar experiences with some jazz musicians. What people seem to fail to realize across many genres is that freedom is not license. Listening is far more important than playing.
It's easy to categorize people according to stylistic pigeonholes and then apply stereotypes, but the truth in my experience is that in every area of music you will find extraordinary people who truly listen and live in the moment and are able to express that musically. It transcends genres and all social boundaries.
I used to play in a band here in Boulder called Headgear which was led by a guitarist who had spent 20 years composing some highly idiosyncratic music with many through composed sections interspersed with absolutely free improv. Aside from myself, there was a classical violist and a drummer who halfway through the project abandoned the drum kit for a full-time commitment to tabla. It was an amazing experience to spend lots of time with them creating a common language, working on the written out parts and also working on conceptual improv (what does this picture sound like? How do we link concepts like ocean travel and an unmade bed in a musical piece?).
One of my musical highlights was playing John Zorn's musical game, COBRA, which involves a very complex and delicate structure, requiring that the players be able to leap not only styles and genres but roles applicable to their instrument. One aspect is that in the course of the game, you might be called on to take over the musical role played by another. How do you play a drum part on the bass? A DJ part? A trumpet part infused with harmonics? In the performance in which I was involved, the players ranged from hip hop DJs to classical and jazz horn players, to ethnic musicians (bazouki, tabla, etc.) to rock musicians to jazz players. Everyone was of a very high caliber and at the conclusion when we were packing up, I got perhaps the greatest compliment of my life. Ron Miles, trumpeter extraordinaire and frequent collaborator of Bill Frisell, came up to me and declared that I had big ears.
Bill, I remember seeing Zardoz at an art theater back in 1979 or so in a double feature with A Boy and his Dog. Great use of the 7th Symphony!
I started playing classical music around the age of 3 or so and ended up with 10 years of oboe playing, so I got great experience doing everything from orchestral playing to chamber music, from renaissance to modern. Learning how to rehearse and perform in a chamber group does wonders for your ability to play in a rock band!
My grandfather was a post 12 tone modern classical composer of piano music (and compatriot of Elliot Carter, Arthur Berger, etc.) so I grew up hearing some really weird stuff that I accepted as music. It's interesting to hear music that is incredibly carefully structured that sounds like improvisation!
OK, enough rambling.
