WASHINGTON, June 6 — When the Beatles broke up more than 50 years ago, devastated fans were left yearning for more. Now, artificial intelligence is offering just that.

From “re-uniting” the Fab Four on songs from their solo careers, to re-imagining surviving superstar Paul McCartney’s later works with his voice restored to its youthful peak, the new creations show off how far this technology has come — and raise a host of ethical and legal questions.