Macy Gray introducing her set with "Hello Sydney" was a sign of things to come as hundreds of disappointed fans walked out on the singer-turned-DJ's disastrous Wednesday night gig in Perth.

Promoters of the American star's tour were forced to issue a public apology to guests on Thursday morning after Gray arrived on stage at the Astor Theatre gig two hours late, sung two songs and DJed for around half an hour before leaving.

Macy Gray's Perth show was a disaster. Credit:Instagram/Helena Kenny

The apology comes three days after the 48-year-old singer issued a personal letter to fans apologising for disappointing guests at a Bali gig over the weekend – promising to "make it up to them" if they came to one of her Australian gigs.

"I apologize [sic] that so many of you were disappointed. Of course, that was not my intention. I won't bore you with explanations or excuses because they don't matter anymore," she said.