Easy listening (also known as orchestral pop) is a popular music genre and radio format that was most popular during the 1950s to 1970s. It is related to middle-of-the-road (MOR) music and encompasses instrumental recordings of standards, hit songs and popular non-rock vocals. It was differentiated from the mostly instrumental beautiful music format by its variety of styles, including a percentage of vocals, arrangements and tempos to fit various day parts during the broadcast day. Easy listening music is often confused with so-called elevator music provided by Muzak Holdings and other music services for malls and elevators, or lounge music, but while it was popular in some of the same venues it bore only modest resemblance to the background sound of this kind of music. A significant portion of easy listening music is purely instrumental and included some big band and orchestral arrangements of standards, themes from movies, bossa nova hits and small instrumental ensembles playing instrumental versions of popular songs, including light jazz and even some soft rock and roll. Orchestras and groups included Percy Faith, André Kostelanetz, The Melachrino Strings, The 101 Strings, Henry Mancini, Herb Alpert, Stan Getz, Antonio Carlos Jobim and Paul Mauriat. Vocals were by the popular artists of the day such as Frank Sinatra, Tony Bennett, Matt Monro, Jack Jones, Barbra Streisand, Vikki Carr, Dionne Warwick, Nancy Wilson and others, and vocal groups or duos such as Simon & Garfunkel, The 5th Dimension, Harpers Bizarre, The Lettermen and The Sandpipers.