Playtest Process
From RBN/C3 Documentation
There's a lot of content in a single song, and we don't expect anyone to look at every part of every song. Of course, you're more than welcome to do that, but don't feel obligated to do more than you can handle. To make things easier, we've separated each review section into individual pages for easier consumption. Enjoy!
Keep in mind one important Audition Mode term, "MBT". This stands for Measure, Beat, Tick. If you see an MBT on the screen of 23.3.120, that means that you are currently at measure 23, beat 3, 120 "ticks". These 120 ticks represent a sixteenth note into the beat. If you don't know specifically what all this means, that's fine. However, making a note of these MBTs (or a rough estimate) will make the author's life a lot easier. These MBTs will tell the author exactly (or roughly) where the issue appears in the midi, so fixing any errors you find will be a lot easier for them. To make reading the MBTs a little easier for you, there are a few actions available on the standard Xbox controller, listed on the Audition Mode page.
Also be aware that you can adjust the volumes of the instruments and the crowd using the in-game menus under Options->Audio. This can help isolate the particular instrument you are testing.
Playtesting Standards
We have very strict standards for how we want Rock Band Network tracks to be authored. Your job as a Playtester or Peer Reviewer is to make sure that the song's creator has done a good job of making the song play properly and represent the music as much as possible. The pages linked below are a good list of things you should check to make sure the song is ready for RBN.