How do CBS get ready for an improv gig? Do such preparations fit with the idea of it being an improv gig at all? Its a question of degrees: To what extent are you improvising?
If the improvisations are truly open you start playing and go where the music takes you, trusting in that journey and in the players that you are working with etc. Thinking about pre-defined points on the journey doesn't come into it.
However CBS doesn't work in that way. We use a short minimal list of 'cues' - spurs, ideas, even a phrase... The aim being that there is enough openness so the group can explore without feeling restricted but enough structure and ideas to make for an interesting set of music e.g. 'bowed section' or 'C groove'. There is no doubt that knowing what these cues are in advance gives the players, some of whom are not very experienced improvisers, more confidence. I would say this is particularly true over pitch and sequence recognition.
In the past I referred to the cues as stabilisers; something I thought we needed to get us started and would then come off as the project progressed. We did try this and did sets working without cues however this led to long dirge like jams often stuck on a single chord. The music lacked any sense of movement, change or contrast. This was a disappointing and difficult period for the project. One where its musical direction had to be re-evaluated. Clearly I could have persevered and done exercises to try to get the group playing good free improv (with no cues.) However through speaking with the players I realised I was trying to take the group somewhere they really didn't want to go musically and that actually this was equally true for me: 'Free Improv' was somewhere I'd thought I'd want to go to the exclusion of all else but then realised that much as I like elements in that music, the timbral exploration, the energy, the unpredictability et al. traditional use of pitch, rhythm and grooves, elements not normally associated with free playing, were things I liked musically and that the band did really well = CBS incorporates elements of free improv but is not be governed by its limitations.
This took me back to improvisations that I had really been inspired by and wanting to further understand them. Looking at groups like Cream it was pretty clear that to some extent they were working as a traditional jazz band - using the set material or framework as a jumping off point for improvisation. They were top players, very good at 'riding the bike' so these frameworks were not stabilisers = This is a style of music in itself, not a staging post to free improvisation. I felt this gave me a green light to continue to use the cues. To cherry pick potent elements and bring them to CBS from different idioms = pan-idiomatic.
The CBS cues have been explored in rehearsal. This gives a sense of how potent they are as ideas and thus roughly how long they might go on. I then select a list of maybe six cues to do an hours worth of playing. These are put into an order ...explaining how this is done belongs in another post.
Onstage in my directors role I try to let the music take its own course, to encourage and support and to intervene (through playing or visual signals) only to move sections, to encourage players (which maybe suggesting soloing) or to change dynamics e.g. drop for a quiet section. To make it work this approach requires that the players are willing to trust and take that direction. As always, it is key for everyone to be switched on, aware as to what the other players are doing.