Medford nonprofit Down By Riverside invites you to The Longest Night, a winter solstice event featuring soul and blues music at Arts Collaborative Medford. Down By Riverside founder Hendrik Gideonse and Brad Faucher, a first-call guitarist and vocalist on the Boston blues, jazz, and R&B scenes, will improvise together and then play through a bunch of old classic blues and soul music. Then they’ll invite musicians to join them, so bring your axe if you would like to join. The event is pay what you can, with a $10 donation requested to defray costs of the potluck.