Kerry-Anne and I visited Zula Sound Bar for the first time a few years back when Freshlyground was still largely unknown. It was their night to perform, and the intimate setting at Zula was amazing! Zula is practically an institution in Cape Town and definitely worth a visit (unless you can't take very crowded and vibey places :) ).
Each night Zula (in Long Street) rocks its patrons with the sound of a variety of live musicians. From what I've heard they have really good traditional food (like potjiekos, boerewors rolls and sosaties), and they also have half-price cocktail specials between 5pm and 7pm, Monday to Saturday.