Friday and Saturday nights we had a live DJ for a few hours a night for atmosphere, but I honestly don't think it mattered much one way or the other. People would have showed up anyway.
We tried boosting Mon/Tues night, but nothing made any difference at all on Monday, and the difference on Tuesday didn't cover the costs. We pretty much considered Monday the paying-your-dues night, and had fun amongst ourselves and the handful of regulars and closed at midnight (vs about 2 am on other nights).
One thing about the non-fri/sat nights, there's a definite trend of "them that's gots, gets" in the bar scenes on those nights. People go where people are, so it's not a linear function on those nights, it's discontinuous. Once you have a crowd, you get a crowd. Weekends are different, there's crowds everywhere.