an Entity references as follows:
"Once in a Lifetime" is a 1991 single by Gregorian from the album Sadisfaction. The song is sung by the Sisters of Oz (Susana Espelleta and Birgit Freud). The singles were released on both CD format and vinyl in 7" and 12" versions. An exclusive remix named "Summer Mix" only appeared on the vinyl version and was never released on CD format. The song was later covered by Sarah Brightman, Princessa and in Cantonese by Shirley Kwan.