The four piece band was the early rock and roll success formula. Lead Singer, guitar, bass and drums was the standard outfit, often with a lead singer playing rhythm guitar and/or harmonica. Shortly after rock and roll started to make an impact a fifth person on keyboards was added, sometimes replacing the need for a rhythm guitar. In the beginning the formats were depending on 2 factors:
The financial split and the stage space available in clubs and venues. Many of the original rock and blues venues had no entertainment budget and loosely allocated a percentage of the tap for the band. Obviously smaller outfits had a better share. The better and more all around the guitarist was, the less members the band needed. Also the space allotted for equipment was a major factor. Bands needing huge equipment space were in lesser demand.