"The first two criteria are quality and popularity. The next factor is whether the song has been on a previous recording, and if so, how long has it been since that recording was published (we try to keep things fresh and new). Lastly, we try to get as many people doing solos as possible, but sometimes the first three criteria limits who can solo on each cd so that not everyone has a recorded solo."
Makes sense to me.
Now, go and head on to Brandon's YouTube channel to check out his videos and show him some Octet-love. (He solos in "Somebody's Crying" on his page and has an incredible voice!)