Chris Brown Making Songs In Jail With Fellow Famous Inmate, James DeBarge

Chris Brown is feeling the Rhythm of the Night … with the guy in the next cell.

The most famous inmate at L.A. County Jail is passing his time singing tunes with the 8th (we're generous) most famous inmate — James DeBarge.

The two R& B stars are locked up in side-by-side cells — in the segregated unit for high profile inmates.

TMZ reported they've been collaborating on music and have already written three songs, performing them during the long days … with other cellmates harmonizing.

This is kind of amazing … they can't see each other. It's all about the sounds.

You know why Chris is behind bars. As for DeBarge … it's all about those pesky drug convictions.