Western popular music that generally predates the advent of rock and roll in the mid-1950s
Traditional pop (also known as classic pop and pre-rock and roll pop) is Western popular music that generally pre-dates the advent of rock and roll in the mid-1950s. The most popular and enduring songs from this era of music are known as pop standards or American standards. The works of these songwriters and composers are usually considered part of the canon known as the "Great American Songbook". More generally, the term "standard" can be applied to any popular song that has become very widely known within mainstream culture.
Traditional/classic pop music is generally regarded as having existed between the mid-1940s and mid-1950s. AllMusic defines traditional pop as "post-big band and pre-rock & roll pop music".
Read more or edit on Wikipedia