I used to avoid like the plague unstructured, free form jamming, I just didn't feel I was good enough and I didn't have nearly enough chops to contribute effectively so it left me cold. More recently though, a jam just kind of happened in the rehearsal room - the sax player was having a noodle to himself and gradually everyone just joined in and it became quite a funky thing IMHO, might even be the start of an idea for a new song. Not only did I manage to carve out a riff or two in the 8 or 9 minutes, I managed to change the direction of the jam as alluded to above, I went for a change about 6 minutes in and to my surprise (and delight) everyone followed me (there or thereabouts)!
There is a recording, I swithered about putting up stuff that isn't "ready" but seeing as I think it's relevant - here it is: [media]http://www.ifb.co.uk/~matthew/mp3/Teaspoons/practice20141118/Funky%20Spoons.mp3[/media]