I was in the area around 6pm on a Friday in the summer and I found 3 places with live bands playing. I have no idea when they start. You could contact the venue and see if they have a playbill for the evening.
My best guess, if you are going to Beal Street on a Friday or Saturday night, the major places like this one will have a blues band playing, even at 6 pm. Just walk down the street, you will hear them.
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