The main tool, in my experience, for improving a band's performance over time is implimenting a click track. If you're already running an in-ear rig (avioms, wireless IEM's, etc.) there's no reason in my mind why click shouldn't be a part of what's happening. And I'll get to some reasons. However, if you don't have money for personal mixers for each player or professional in-ear systems for everyone on stage, there are some less expensive ways it can be done. When I was in