The Medley Leader is the Fraggle chosen to start the medley with their inner song. It's a musical tradition that is carried by Cantus and the Minstrels as they wander Fraggle Rock.
In the episode "The Minstrels," Red volunteers to lead the Fraggle medley, initially mistaking the term "medley" as a race rather than a mix of songs. Unlike her friends, Red has trouble finding her song, although she's reminded countless times to listen to what's inside her.