If you are in the muse union. Its a good idea to let any studio /producer know before turning up to do session work. Some can be 'a little frosty' due to bad experiences. Like in the middle of a recording the mu members get up and leave mid take for their tea break. Or start whining on about what the music will be used for and demanding endless paperwork filled in. Had one experience when the studio owner and producer pulled the plug on a session and flew to czech republic to do it instead. Dont get me wrong I think its a good idea to have representation but mu is mostly for state funded orchestras, military bands, bbc etc basically anywhere that is paid for by government. Walk into your local pro recording studio or venue and tell em your in the mu and see how it goes down. Usually a big (closed mouth) smile, followed by a moments silence and then a 'how interesting'! is the response.