In the age of ProTools and digital recording, the art behind making and recording records has changed considerably. For example, today when a producer needs a certain embellishment or accoutrements that the band itself may not be able to provide, he can simply open a pre-made sound file or use a computer to create the sound effect. Yesterday, however, those flourishes (and often times, the entire song or album) were provided by session musicians, hired to perform either a small bit part or to help complete the entire project. These musicians were rarely considered part of the band and, until the Muscle Shoals Rhythm Section, only got paid for services rendered.
Most session musicians never became famous or held the limelight, though there have been a few who went on to bigger, more famous careers: Phil Collins began as a session drummer; Duane Allman, Glen Campbell and Jimi Hendrix were all session guitarists; Billy Preston on keys; and of course, some of the well known groups such as Booker T. & the MGs (Stax Records house band), the Wrecking Crew (an LA group associated with Phil Spector), the Funk Brothers (Motowns session group), and the previously mentioned Muscle Shoals Rhythm Section (one of Jerry Wexlers personal favorite groups and the first session group to earn points on every record they worked on). The Kinks Ray Davies said, Session players are for the most part, anonymous shadows behind the stars. They do their job for a fee and then leave, rarely seeing their names on the records. Their playing never stands out, but if you take them out of the mix, the track doesnt sound the same. You only miss them when they are not there. The personification of that quote might best be found in session pianist Nicky Hopkins.