I like to join in on the weekly backing track challenge, I've probably done around 20 and I noticed something about my playing, I was 90% of the playing better after 2 to 3 hrs of floundering, I take a break and let the blood flow again, say hi to my cats, and when I come back I usually play the best right away. My point is, I have memorized the bt, not for scales and such since that usually gives me zero problems, my problem is hearing the song that could be sung, the points where chord and scale merge. No need for scales, imo that's the stuff I strive to move on from, in success that is. So every bt gets memorized by ear before I play. Being under the pressure of recording a good solo within one week is the challenge. Now maybe you're talking about memorizing a tune, in that case disregard the ramble above, or not. Go over to Twanger Central and record this weeks bt, it's a real nice one, and it is an opportunity to achieve in more areas than just memorization.