Apostrophe can be used to show that one or more letters were ommited.
So, it could be:
pick ’n’ mix - short for pick and mix. (here, the elision of "a" and "d")
rock 'n' roll.
On the other hand, normally "and" wouldn´t be elided into "N´" as in Guns N´ Roses. But then, in the music scene everything is allowed, so nobody will sue you if you use such elisions. By the way, you can see music titles like "Day 'n' Nite", the use of apostrophes in a unconventional way would be small potatoes in such domain (that of music).