You need to be in Quickplay+ for this achievement. A standard band is a band with no duplicate instruments, e.g. you can't have two guitars. I presume it can be done on "Bleed it out" by Linkin Park with an expert guitarist and expert bassist. On "Bleed it out", for the two gold medals in a standard band you need to hit 1,070+ notes and score 170,000+. You should do this achievement early in the game because you will need a song that has no medals earned on the band challenge. It can be done however on any difficulty.