Among the most important architects of The Motown Sound were the members of Motown's in-house team of songwriters and record producers, including Motown founder Berry Gordy, William "Smokey" Robinson. Also instrumental to the sound was the work of Motown's in-house band, The Funk Brothers, who performed the instrumentation on nearly every Motown hit from 1959 to 1971.
The Motown producers and the Funk Brothers band used a number of innovative techniques to develop the Motown Sound. Many tracks featured two drummers instead of one, either overdubbed or playing in unison, and three or four guitar lines as well.
The Motown Sound was also defined by the use of orchestration, string sections, charted horn sections, carefully arranged harmonies and other more refined pop music production techniques. It was also one of the first styles of pop music of that era wherein girl groups--including The Supremes, Martha & the Vandellas and The Marvelettes --were showcased as an act, as opposed to individual female artists.
Source: Gerri Hirshey's "Nowhere to Run: The Story of Soul Music." (1994)