I can't believe I forgot about this one! I have updated my list to include this great muppet feature. Thanks to my brother Nick and commenter Mandy for the reminder.

Emmet Otter's Jug-Band Christmas (1977)

On TV? Not sure

Though Emmit Otter's jugband was pretty good, in a folksy lo-fi sort of way, nobody can deny the awesomeness of the Riverbottom Nightmare Band: