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The Band Perry's Kimberly Perry says things "really jelled" between her group and Fall Out Boy during their final rehearsal for "CMT Crossroads."  But members of the country trio and the rock band both admit it took an effort to get to that point. 

The Band Perry's Neil Perry tells Nashville's "Tennessean" they found Fall Out Boy's material tough to pick up, because the rockers' songs are structured differently. 

Fall Out Boy also had some difficulties with The Band Perry's music.  Fall Out Boy frontman Patrick Stump says The Band Perry's current hit, "Don't Let Me Be Lonely," was particularly tough for him.  But he adds that overall it was "a cool challenge" to learn each other's songs. 

The Band Perry and Fall Out Boy's "CMT Crossroads" set features four songs from each group as well as a cover tune.  The hour-long show will have its premiere on CMT Friday at 11:00 p.m. Eastern. 

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