I can't really think of a better title for this, because there are many topics here and I don't think they need to be separated into individual little threads.
Composers/writers
Right now, song pages use the official CD credits where available, but album pages still use the iTunes composer credits. In my opinion, iTunes is a fine source in lieu of CD credits, but if available, the CD composer credits should also be used on album pages.
Durations
We need to agree on a consistent source for song durations, because the durations on iTunes are often off by a second or so from what's listed on the wiki. I'd suggest just consistently using iTunes for them.
Performer credit order
Where CD credits are available, I think we should change the order of performers in the lead, infobox etc. to the order they are listed on the CD.
Translated titles
Most translated titles seem not to capitalize every word now, but there are exceptions such as "Eres". I'm undecided on this, but we should be consistent.