The Title of the song is 'The 59th Street Bridge Song' aka 'Feeling Groovy' by Angie Stone. (Yes it is a Simon and Garfunkle Song- they wrote it). If you want to see the commerical:
1. Go to www.gap.cpm
2. click on 'women' to go to that department
3. a menu should appear below the large pic. it should say 'Fit to feel groovy' there is a link below it the says 'See Spring TV Ads' or something like that.
4. On the page there are two commericals, it is the one that says 'Frankie's Look'.