“One” is a song written by Harry Nilsson. It appeared initially on “Aerial Ballet”, Nilsson’s third album. The song appeared initially on Aerial Ballet, Nilsson’s third album. Harry Nilsson wrote “One” after calling someone and getting a busy signal. He stayed on the line listening to the “beep,beep,beep,beep…” tone, writing the song. The busy signal became the opening notes of the song.

In 1968, Al Kooper released the song on his debut album I Stand Alone.

In 1969, rock band Three Dog Night covered the song on their debut album Three Dog Night and reached number 5 on the Billboard chart.

The song was covered by Aimee Mann for the 1995 Nilsson tribute album For The Love of Harry: Everybody Sings Nilsson.

Dokken, a 1978 heavy metal band also covered the song in their 1999 album, Erase the Slate.