The lockdowns associated with current coronavirus pandemic have sparked production of self-duets. The Austrian-German concert violinist Augustin Hadelich has released a lot of piano-violin self-duets on his YouTube channel.
Back in 2016, fiddler Katy Adelson produced this interesting cello-violin self-duet -
Self-duets predate the YouTube era. Back in 2006 on the album "You Raise Me Up: The Best of Aled Jones" there was a track featuring the adult, baritone Aled Jones accompanying his younger treble self on his 1985 hit "Walking in the Air".
Is this the earliest recorded self-duet? Have many musical artists been producing self-duets before lockdown?