Maybe I missed something here? I don't see the makeup of your band. 2 guitars, keys, drummer. 3 piece, 5 piece? It would make a difference if I had that problem. I'd go around him on starts by using someone else. If he couldn't follow the group, I'm afraid he would have to be replaced. Friend or not bands are a business. Supposed to be fun but, you are at work. I don't know of many businesses that put up with substandard employees for very long.
This will sound rude but, from my standpoint as BL, if after 3 years and you are BL, and the problem still remains, you created the problem by not handing it as soon as it became one. Friend or not, a band is only as good as it's weakest link.
This will sound rude but, from my standpoint as BL, if after 3 years and you are BL, and the problem still remains, you created the problem by not handing it as soon as it became one. Friend or not, a band is only as good as it's weakest link.

