The problem I was getting at a bit was that regular sessions, musicians planted in the usual pubs will by definition have an element of being their for attracting, let's call them, visitors. While local musicians playing for their own amusement will do so without telling you about it, unless they know you well enough.

I would suggest it's best to rely on local knowledge, word of mouth, once there for what's happening on the day(s) rather than the pre-planned nine months ahead thing. There's a lot of nice music and song in Galway. And it's a lovely place too, very busy at that time of year though, it's a right tourist destination. ;-)