Dana Lusk did a seminar on Irish session etiquette at the recent Colorado Irish Festival, admitting that she, like many of the audience members, regularly broke the rules she laid down. But even if the rules are followed more in the breach than by their observance, you'll find yourself ruffling feathers if you don't at least know what they are. That's why one of the first rules of the Irish session is to sit and listen at first, and try to get yourself invited, rather than just jumping right in, as you might at a jam session.
There are two types of sessions in this sense, open and closed. A closed session is limited to those participants who have played together for some time already, while anyone may play at an open session, provided they get permission, explicitly or tacitly from the session leader.
Even audience members can commit faux pas at an Irish session if they're not careful. While it's completely acceptable (and even welcomed) to cheer and applaud at the end of a tune set, and buy drinks for the musicians, conversation should be kept fairly quiet while the music is playing, and it's not OK to shout out requests, especially for “Free Bird,” or its Irish music equivalent “Danny Boy.” Unlike the American bar scene, where the music is so loud you have to shout to have a conversation, an Irish pub, where most sessions occur, is a community gathering place where a quiet conversation is part of the craic (pronounced “crack,” it means fun, conversation and fellowship)
Community is really at the core of pub life, and a key to the session experience. In an American bar or tavern, the main objective is to drink and meet people of the opposite sex. In a pub, Irish, Scottish, British, or the like, the regulars form sort of a community, and you can make lifelong friends in a pub. The best pubs are part of the neighborhood, an extension of village or community life. Back home in Ireland, a few locals who had grown up together would gather at the pub to play a few tunes and have a few pints together. From this came the seisún, and it bears the marks of its origins even today.
Session music was traditionally learned by ear, passed along from one musician to another. Because of this some very strict sessions frown on the use of sheet music to learn the tunes, though others are very open to that practice. If you're a musician who wants to get into session music, be sure to learn the local custom before bringing your tune book to a session. And really, there are intricacies in traditional Irish music that cannot be expressed in standard notation, so even if you learn the tune from a written source, listen to how others play it for the enhancements they can supply. Of course, each session is different, and they may a tune slightly differently from the way other session players do it, so keep that in mind if you play in more than one session.
Certain instruments are common to session music, such as the fiddle, Irish flute, tin whistle, mandolin, Irish bouzouki, Uilleann pipes, and bodhrán. Others come up from time to time as well, such as the tenor banjo, guitar, accordian, hammered dulcimer and others. Many session players would frown on the use of non-traditional instruments in a session, but there are talented players who have made them work and gained acceptance. But this music is largely governed by tradition, (It's often called TRAD by devotees.) and innovators have to work hard if they want to overcome the habits of decades.
It's a common misconception that the bodhrán, an Irish frame drum, is easy to play and thus the perfect introduction to session playing. It's easy enough to keep a steady beat if you have enough rhythm, but the instrument has subtleties that are not apparent to the casual observer, and experienced session musicians will spot you for an outsider in a flat minute. The same might be said of guitar players who don't know Irish session music. The chord patterns can be quite simple, but how to integrate your guitar with other session musicians can be tricky. It's also traditional for only one percussionist or one guitarist to play at a time, as these rhythm instruments can easily overcome the melody, and that's never good.
Getting into session music, or even attending one, can be a tricky adventure, but a rewarding one. There's something about Irish music that reaches the soul, no matter what your background. Check the list on the right hand side of this page for some local sessions, stop by and see what's up. Maybe you'll be hooked too.
For more info: Check out Field Guide to the Irish Session by Barry Foy. Its rules are too legalistic for some people, but it's a great general introduction to the subject.