All you need is:
- All the instruments of course (x2 guitars)
- Two people who are capable of playing easy and not missing a note, you'll need one who is good at looking at both Bass and Guitar at the same time
- Either online play or have the song Charlene downloaded.
Basically if your trying to get this achievement all you need to do is put all instruments on easiest difficulty on the song Charlene.
Get one person to play guitar and bass (on the easist difficulty you only have to strum) fortunately the bass and guitar works very well together you'll find that the guitar and bass normally needs to be strummed either at the same time or 1 second apart from each other (so you'd strum guitar, then bass, then guitar, then bass but it is very easy)
The vocalist doesn't need to even sing as they automatically get 100% on the easiest setting - if this is not the case...put it next to a loud constant noise like a hair dryer or the tv (might get HORRIBLE feedback doing this so take turn mic voice volume off in options)
Drummer just needs to hit one pad at the right beat on easiest difficulty (it shows different notes but you only need to hit it to activate it) leave star power unactivated if you are having trouble with this.
So to recap
1 person plays guitar and bass (or get a third person)
1 person plays drums
0 people need to play vox
if you cant unlock this...there is no hope for you!