Rio is a 1982 song by Duran Duran that appears in Band Hero. The song is widely regarded as being the most difficult due to it's intensity, and that is widely true.
Intensity:
Guitar: 40%
Bass: 60%
Drums: 70%
Vocals: 70%
Tier (Career) :
All Career - 8.Red River Canyon (Encore)
The bass pattern on Expert is very tricky to FC, using a variety of HOPO notes inbetween bass notes, the player has to incorporate double strikes. This is what gives the song it's signature trickiness.