Question: Who most commonly sang the fastest-selling single by an Australian artist as a duet?
Sentence (from "Anthony Callea"): Callea's debut single "The Prayer" is the fastest-selling single by an Australian artist, held the No.1 spot on the ARIA Singles Chart for five weeks, a record for the debut single of an "Australian Idol" contestant, and was the second-highest selling Australian single of the last decade.
Relevant evidence: Yes