 A Public Service Message From Your Old Time Bass Player
Greetings old-time jammers! I’m Larry, and I’ll be your bass player tonight. Before we get started, I’d like you to know that I always endeavor to play exactly the right note at exactly the right time, on every tune, no matter how obscure or crooked it might be. But in spite of my best efforts, during the course of tonight’s festivities there is a small chance we might run across one or two chord changes that I will not interpret to your satisfaction. If and when this happens, I welcome your suggestions, as long as they conveyed in a positive, musically appropriate manner.
For example, yelling out something at random like “There’s a II chord in there!,” especially when delivered in a scolding tone and with a frown, is neither musically helpful nor polite. Instead, try catching my eye, then say something like, “Hey Larry! Play … an … A … right … here!, indicating the desired change at the appropriate moment with a clear left-hand motion and maybe a nod. That way, you’re telling me not only what note you’d like me to play, but more importantly when.
Even better, if you know the piece you are about to kick off has an unusual or non-intuitive harmonic or rhythmic structure, consider throwing your poor bass player (and everyone else at the jam) a bone. “This one goes to an E chord in the B Section” or something like that is all it takes. This is even more important if you insist on playing some obscure fiddler’s version of a common jam-standard tune. It’s quick, easy, advances the music, and doesn’t make people (okay, me) feel like an idiot. A win-win!
Finally, consider approaching these situations with a bit of humility. It’s possible – unlikely, but possible – that what I am playing is “right,” and the chord you are calling out is nonsense.
Now let’s enjoy the jam, and play nice! | 
