'American Idol' Ringtone: Sue, Sue, Sue Me

"American Idol" band members are suing the hand that feeds them because, according to legal docs obtained by TMZ, they're being grossly underfed.

In a federal lawsuit filed Friday, the American Federation of Musicians claims American Idol Productions made a deal with the band on the show which makes the tunes the whole world sings -- a deal that prohibits "Idol" from cutting the band out of downloads and ringtones of the music played on the show.

Short story ... Since the 4th season "Idol" honchos have been "selling digitally-encoded audio files containing those soundtracks." The suit claims some of the audio files were sold as songs and some as ringtones.

According to the suit, "Idol" execs never got permission from the musicians to make the sale, in violation of the union agreement..