Producer John Fields filed the lawsuit in L.A. County Superior Court, claiming he produced a total of 9 songs for Bell's new album "A Reminder" back in August 2010.
According to Fields, Bell agreed to pay $9,000 for every song Fields produced -- but only ended up paying for five.
Now, Fields says Bell owes him the balance -- $36,000 -- and he's suing to get every penny back.
Funny ... of all nine songs ... only four made it to the album, which was released last year.
Yeah we didn't hear about it either.