For the first week on Idol the Top 24 has been challenged to sing Top 10 tunes from Billboard's Hot 100.

However, the Idol semi-finalists haven't been given free reign on that gigantic theme, there are some year restrictions. The Top 24 will be able to choose Top 10 tunes from the following years: 1958-1972, 2004, 2005, 2006, 2007, 2008, 2009 and 2010. 

I'm sure Tyler Grady is bummed that most of the 70s aren't available for him to choose from and there is no word yet why the 80s and 90s were completely ignored. Perhaps they're saving those songs for later themes and mentors? An all 80s week would blow this child of the 80s mind. (Lilly Scott signing Cyndi Lauper? Sign. Me. Up.) There's good news for the acoustic guitar slingers and piano players of the Top 24, instruments will be allowed during next week's performances.

http://www.buddytv.com/articles/american-idol/american-idol-and-the-top-24-t-34729.aspx