I've been thinking of putting a pickup in my banjo simply as an aid to tuning during noisy sessions: I've got a little HoneyTone amp with a mini-headphone jack. I suppose I could also pull the headphones and amplify on the sly to give me a chance against resonater banjos played with picks, mandolins, fiddles, etc. (I play clawhammer openback without picks), in Irish sessions (of course, I have to learn the tunes, too).

--seed