The longest marathon whistling lasted 25 hr 30 min 5 sec by Jennifer Anavi Davies (Canada) at the Impossibility Challenger in Dachau, Germany, on 2-3 October 2010. She rotated among a selection of 125 different tunes, each at least 2 minutes in length.
Davies had previously attempted unsuccessfully to set this record. This was her second career attempt.
Comments below may relate to previous holders of this record.