In a night of star-studded pairings – from Rihanna
performing with Sugarland to Reese Witherspoon
presenting with her Water for Elephants
costar Robert Pattinson
– Sunday's Academy of Country Music telecast will get a double dose of American Idol
judge Steven Tyler is expected to join former Idol
winner – and country superstar Carrie Underwood
– at the awards show, PEOPLE has learned.
According to a source, the pair will sing a duet.
The ACMs will air live on CBS starting at 8 p.m. ET.