If the test footage is really good, you can include it. However, (and I'm stealing this advice from Smeagol here) if on a scale of 1 - 10, the footage is a 5, but you know you have more footage that's a 6, leave out the 5 and include ONLY the best. No need to clutter up the reel with mediocre work if it's not really really good (now, some tests are super good, some even better than features, and I included a test in my reel because I felt it belonged. It depends on how it looks and if it's quality work. You made it, so feel free to add it.)
As for music, just pick something upbeat that you like. I'm unsure about vocals, I think they probably take away from the work.
As for length of a reel, it should be about 2 minutes, max. Always put your best work first, because most people won't stay for the ending (which is why you keep it short and sweet).
YouTube • Website"Whatever you do, do all to the glory of God." - 1 Corinthians 10:31b