There isn't much to say on this, but you can speed this up by going to the Extras menu option and turning on Short Create. This will let you record shorter versions of songs. I did this while I was working, so I wasn't even in front of the kinect most of the time.
There are 40 songs in the game so if you go down the list you'll get this a bit over halfway. You'll need to do another 25 for this achievement: