Some of the information in these postings is pretty good, and some of it is not quite correct.
Permission, for example, is only required when you seek to be the first to record a song. Till it's recorded, it's up to the writer to give or withhold permission. Once recorded, though, the writer HAS to give permission -- it's called "compulsary license" -- and the new recording's publishers (record company, performer, etc.) has to pay the statutory royalty ($.07 / copy manufactured) to the writer(s). Now, this weekend, I was talking to Sandy Paton, and he said there was something new in the recent change of the law (which also extended copyright from 50 to 70 years past the writer's death, to match the rest of the world) which required permission to record anything already recorded (in effect changing the "compulsary license" part of the law. I'm asking around the songwriting community for more on this subject, but no results yet.
As for performing a copyrighted song, if it's on a record, you can play it, sing it, whatever, wherever you want. The venue is supposed to pay any royalties due for such performance (which gave rise to the contretemps last year or so with ASCAP & BMI coming down on the Girl Scouts for using copyrighted campfire songs). The rules can seem contrary to reason, sometimes, but that's how it works.