Michael Edward Mills is an American multi-instrumentalist, singer, and composer who was a founding member of the alternative rock band R.E.M. Though known primarily as the bass guitarist and backing vocalist of R.E.M., his musical repertoire also includes keyboards, guitar and occasional lead vocals. He contributed to a majority of the band's musical compositions and is the only member to have had formal musical training.

William Thomas Berry is an American musician who was the drummer for the alternative rock band R.E.M. Although best known for his economical drumming style, Berry also played other instruments, including guitar, bass guitar and piano, both for songwriting and on R.E.M. albums. In 1995, Berry suffered a cerebral aneurysm onstage and collapsed. After a successful recovery he left the music industry two years later to become a farmer, and has since maintained a low profile, making sporadic reunions with R.E.M. and appearing on other artists' recordings. His departure made him the only member of the band to not remain with them during their entire run. Berry eventually returned to the industry in 2022.