Jackson Rathbone mentions Rob in a new interview

SNMag: What’s your relationship like with the rest of the cast? How do you spend your time on set?
JR: It’s fun because we play a family on screen and so getting to come back and do these sequels is like a family reunion. A lot of us are musicians as well as actors so we’d all get together in the rooms and we’d have jam sessions and make up songs. I’d play guitar and harmonica, Rob would play guitar and sing or Kristen would play guitar.
source  via kstewrobfans