From The Art and Popular Culture Encyclopedia
Easy listening music is a style of popular music and radio format that emerged in the mid-20th century. It features simple, catchy melodies, soft, laid-back songs and occasionally rhythms suitable for dancing. Easy listening music is mostly instrumental (often played on light of tone instruments such as the Hammond Organ, "lush strings," or Ukulele). Some singers, such as Andy Williams, Jack Jones, Engelbert Humperdinck and Eydie Gorme, have vocal styles that are highly compatible with this style. Much of the work of some other pop vocalists, such as Frank Sinatra, Bing Crosby, Tom Jones and Mel Tormé were considered too frenetic or swing-oriented to be played in an easy listening radio format.
Circa 1980, easy listening was the most listened-to radio format in America. However, the easy-listening format gradually declined and became scarce, not because its listeners were too few, but because they were getting too old and therefore less desirable for radio advertisers.