The Oscar-winning actor, who passed away last year, had completed work on an animated promo for indie-rock band Modest Mouse's 'King Rat', as well as directing newcomer Grace Woodroofe's cover of David Bowie's 'Quicksand'.
Ledger's work on 'King Rat', which features animation from his Imaginarium Of Doctor Parnassus director Terry Gilliam, arose after he bumped into frontman Isaac Brock in Australia several years ago.
Speaking to VH1 in 2007, Brock said: "Heath and I have a mutual friend... The idea sort of dropped, but then he just sent me an email saying that he wanted to do it."
Ledger previously helmed music promos for Australian hip-hop group N'Fa, singer Ben Harper and a tribute video for late musician Nick Drake.
Before his death, Ledger told the Los Angeles Times that music had made a huge impact on his life, saying: "It has always been a key that kind of unlocked, or enabled me to express anger, or pain of any sort."
Fans have been told to expect the videos later this year.