As this has been mentioned in a coulpe of threads I thought that I should do a little info thingy on all of the opportunities - I'm sorry if I misss stuff out as I'm not really a player but I know the ground
Orchestras
CUMS I - Cambridge university music society top orchestra. Conducted sometimees by students and sometimes professionally. The repertoire is challenging (the though often a bit 19th century) and the orchestra is about as good as the NYO. Expect to be Grade 8 for strings and stupidly good for wind.
CUMS II - Also run by CUMS this orchestra is not as good but is still quite good. It is conducted by students elected by the orchestra. Not really sure about quality but again winds arre grade 8 + and strings are pretty good.
CUSO - Student run orchestra, almost as goodd as CUMS I *waits for someone to shout at him*. About the same level of playing expected.
CUCO - Student run chamber orcheestra of the players who think they're the best - Part of the string-player fetish for small ensembles. Everyone in this orchestra is stupidly good.
UCPO - University of Cambridge Philharmonic Orchestra - is a non-audition orchestra. TBH it's **** but they spend a lot of time in the bar after rehearsals so that's alright. The repertoire tends to be youth orchestra standards
College Orchestras - some are regular occcurences, some are not. I know that places like Clare have stupidly good orchestras and places like Robinson just fix players for concerts once a term. Also some colleges have shared orchestras like the orchestra on the hill (Fitz, New Hall, Churchill). These are probably worth getting involved with so you can meet like-minded comrades nevermind the music.
Choirs
College choirs vary in quality and are generally either just choral scholars (King's, Trinity, Johns, Jesus I think) or they are a mixture of choral scholars and auditionees. They vary in quality but all are reasonably good. They also vary in commitment. While King's does 6 services a week plus rehearsals, places likee Robinson do two services plus a couple of rrehearsals. Most choirs get some sorrt of payment like a formal hall once a week. Choral scholars get extra payment.
MagSoc - This is a Queens' run non-audition choir. They do lots of big works like the creation, Requiems, other 19th century stuff
Trinity Singers - another big non-audition choir and is pretty good - theey do performances in Trinity Chapel and there is an aassociated orchestra
CUCC - Cambridge University Chamber Choir - small and very difficult to get into. Sometimes thee auuditions givee very strange results like them letting in someone who was completely untrained this year.
Other possibilities
One of the best places to play at Cambridge is in the theatre. There are often musicals or plays which require instrumentalists or singers and auditions tend not to be too heavy and you get cool after-show parties with strange thespy people.
You can always make your own ensemble too although this is quite an effort.
MB