Originally Posted by ANDREMIKE
Some of the M4A songs that I have were bought from Itunes. Why are some songs on itunes M4A vs M4P?
When the iTunes Store started, all their music was M4P. A little over a year ago, iTunes introduced what they call "iTunes Plus" tracks, which are of a higher bitrate (256kbps vs 128kbps) and DRM-free (M4A vs M4P). These were originally sold at a premium ($1.39 instead of $0.99), but eventually the price dropped to the same as other tracks. Originally, Apple only was able to get record company to license iTunes Plus tracks, but recently Apple successfully negotiated with the other major labels to convert their catalogs to iTunes Plus. However, the conversion process is going to take a while, so some major label stuff may still not be iTunes Plus, and minor labels may not have renegotiated with Apple yet.
Apple is allowing people to "upgrade" previously bought M4P tracks to iTunes Plus tracks if available. The upgrade fee is $0.30 per track. The upgrade process doesn't convert the existing M4P file, but instead downloads a new M4A file.
Note that the free download of the week is always a M4P file, even if the album it's from is iTunes Plus. Also, free tracks are not eligible for upgrading.