"Sitting in" is the time-honored tradition of asking to join in and play a song or two with strangers. It is a high stakes gamble. If you are an accomplished drummer, you risk embarrassing the current drummer and vice versa, you under play and embarrass yourself. But there are ways to do it all gracefully and get what you want: musicians to play with.
It requires some courage and a little hubris. But it in the end, it is how musicians announce themselves into a new scene. It is how musicians find others to play with. So, get ready.
1. If you can, go hang out for a few weeks before asking to sit in. Be friendly, at your second appearance the musicians will acknowledge you with a friendly smile. At the third appearance you will be one of the family.
2. Make a note of the repertoire performed by the band. If you know the tunes, great. In a public jam session, the tunes will be standards. I’ve a list here of jazz standards. For Rock and Blues standards try these lists. Blues. Rock. Then go home a learn a few from memory before you ask to sit in. The tune need not be a complicated one, but it you should have it solidly memorized and in your hands.
3. At home spend half your practice time learning the standard tunes of the genre you want to play. Play with the recordings over and over and over.
4. As a drummer learn the grooves of the genre.
5. Practice with a metronome to develop your ear for time.
6. Be humble! Nobody wants to play with a jerk.
7. When you decide to get up their, be fully sober. Save the drinks for later!
8. As a drummer you will have to play a drum solo. Be prepared. My advice keep is simple and uncomplicated, save the fireworks for later.
9. Be fully vaccinated, don't endanger the rest of the band. I know one band personally that spread covid amongst themselves.
10. When preparation meets opportunity music will be made and magic happens.
extra tip: Bring your stick bag and ear plugs!
When I moved to Toronto in my fifties, I put all of these into action. I now play regularly in lots of different scenes: Rock, Jazz, Improv, and more.
If I can help you get ready, call me.
David Story, drummer, pianist, qualified online music teacher