At many seesions it depends on what the core has a personnal preference for & sometimes where the core comes from, they may prefere to play reels & planxtys where others may like jigs & horbpipes. I've never really found polkas to be a strong part of any session. Some sessions discourage singing as some discourage certain instrunments, others wecolme all. Here in Boston you'll find a favorite session for fiddles, for singing, for slow airs & hornpipes, for straight jigs & reels. for the very good & not so very good, for the snoobish. Boston sessions have been home to some of the best, Seamus Connelly, Johnny Cunningham, Jerry O'Sullivan, Paddy Cronin, Joe Derraine, & I've found that it's been most welcoming of new material & new blood & of the very good & the new. Years ago (maybe 20) I had been a regular at a session & would be called to sing, I was new to the bodhran at the time & wouldn't bring it in till I got some experence under my belt, when I did start to bring it in, I'd only play on the slower tunes & play it under the table at that so not to bother the better players. Seamus Connelly (who I consider one of the worlds best Irish fiddlers) began to single me out to back him up or to play louder so I could be heard, it was encouragement, it was not because of my playing abilities, so a beginner can find that even in the company of the best you can find the best company. Barry