Billy Ray Cyrus -- Raising a New Miley Cyrus ... Rocks Live with Noah Cyrus (VIDEO)

Billy Ray Cyrus can't stop, won't stop ... cranking out talented spawn -- he performed live with Miley Cyrus' kid sister in L.A., and it sounds like the family's got a new revenue stream coming.

Noah Cyrus jumped on stage for open mic night at Crave Café … and Billy Ray backed her up on guitar for a few songs. It was no sold out stadium ... but hey, even Miley started somewhere.

The 15-year-old -- who sounds a lot like big sis -- belted out her take on one of Dad's hits ... "Could've Been Me.”