FFXIAH.com

Well what happened is Red Octane and Harmonix worked together under the name of Activision to make the first few guitar heros, then they split ways under separate publishers/producers. However, it was already planned under the guitar hero name to create a multi-instrument band teamplay based game. Unfortunately Harmonix teamed up with EA and beat the GH folks to the punch by creating Rock Band first. Meanwhile, Red Octane was busy buying time and recuperating to create a better version of it (World Tour) while working with Activision still as well as Neversoft.

I might have some company team ups mixed up but that's essentially what happened.