For the Weekend Genius Challenge, we've done anagrams and clues and various wordplay. This weekend, we go musical!

Just like we found lots of percussion introductions in songs from 1980, we found softer openings (piano, acoustic guitar, even ukulele) in a bunch of songs from 1970. So your job is to identify all 15 of the songs in this medley. If you're the first to get them all (or the first to get more than anyone else) you'll win a T-shirt of your choice from the mental floss store. Here's the music file in mp3 format:

You may have to click twice to get the player to work, depending on your browser. There are no obscure songs here... all but one hit Top-20 on the pop chart in 1970. Answer by commenting below, with all your guesses (and your T-shirt choice) in a single comment. You only get one crack at it, so make your guesses count! The correct songs will be revealed on Monday. Good luck!