The POSTunderground is a nonprofit jazz performance space located in the basement of the Brookline Veterans Post, 386 Washington Street, Brookline. Fridays feature live jazz from 7:30 to 11:30 PM. Sundays, 3 to 5:30 PM, feature an open jam session exclusively for high school and middle school jazz players. Food and admission are always free, and the full CASH bar (Fridays only) features veterans post prices.  The POSTunderground exists entirely through the generosity of the Brookline community.