Initially, the vocalists consisted of artists such as Frank Sinatra, Doris Day, Johnny Mathis, Connie Francis, Nat King Cole, Perry Como, and others. The custom recordings were usually <answer>instrumental</answer> versions of current or recent rock and roll or pop hit songs, a move intended to give the stations more mass appeal without selling out. Some stations would also occasionally play earlier big band-era recordings from the 1940s and early 1950s.
What type of covers of pop and rock songs were usually played on adult contemporary?
instrumental