A picture of Mungo Jerry on the same set exists dated 1973.
The date is wrong as Andi is there!
If 1972 it may be Ramsey Lewis - Wade In The Water from 04/05/72, the other MJ appearance on 20/04/72 shows no PP performance, but there are 2 crowd dancing entries! (David Cassidy - Could It Be Forever and Ringo Starr Back Off Boogaloo).
The outfits are probably wrong for Wade in the Water.
And if you're asking me when, I'll say it starts at the end.
I think its safe to say doc that the top PIC isn't wade in the water as I remember someone once saying this routine was done using chiffon and waving it around as a jez guess ,back off boogaloo or possibly t Rex debra