Next weekend sees the return of the Braunston (Northants) Historic Narrow Boat Rally and Canal Festival. Google "Braunston Marina Events" for full details. There is entertainment on Thursday and Friday evenings before the event proper on Saturday 23rd and Sunday 24th June.
Beer tent music in the afternoons features:-

Ramshackle - fine local folk duo (Lionel and Nick Gent) with accordions and voices.
Three Men In A Boat - another good local group, singing and playing more contempory folk material.
Jan   -   singer-songwriter includes some self-penned canal songs.
DPN+1   - quartet featuring old-time jazz, blues, original canal songs and other stuff.

The bar usually stocks good local ales from the cask. There will also be some morris dance sides attending.