Each year there is a general theme and for the past couple of years the co-op has been "developing a jazz repertoire".  A list of tunes and composers can be found here. There is a wide range of ages and ability but the atmosphere is friendly and supportive. The common factor is a love of jazz and a willingness to learn and to make mistakes along the way. One of the features of the co-op are the regular "masterclasses" run by the very best of British jazz musicians.  These sessions are usually free to members.