Music notes: Billie Eilish, Rihanna and more

Billie Eilish has just hit a new YouTube milestone: She's racked up more than 45 million subscribers on her official artist channel. That makes her one of only nine artists who have that many subscribers. The others are, in descending order, BlackPinkJustin BieberBTSMarshmelloEminemEd SheeranAriana Grande and Taylor Swift.

Is Rihanna engaged?  The "Diamonds" singer laughed off an answer about a giant rock on THAT finger on Tuesday and told reporters, "'This old ring?"  Daily Mail says she didn't confirm whether or not she's engaged to boyfriend A$AP Rocky, with whom she's expecting her first child.

Camila Cabello is rocking a mullet, it seems.  She took to Instagram to show off a haircut -- or is it a wig? -- that screams, "Business in the front, party in the back."  Camila's hair is chopped short in the front and on the top of her head while she sports long tresses in the back.  Lil Nas X commented with two fire emojis.

Mariah Carey is taking you to school with her upcoming Master Class on how to use your voice like an instrument.  She confirmed her course runs on April 14 and encouraged fans to sign up now. "I've never let cameras into my musical oasis before—but that's all about to change. My class on the voice as an instrument is coming soon," she teased.  "Hope to see you there!"