Looks like Billy Ray Cyrus is feeling a little nostalgic ... and maybe sentimental, too. Check it out ... the country star gave ex-wife Tish Cyrus a public birthday shoutout ...

Katharine McPhee and her husband David Foster teamed up to stump for Spencer Pratt and trash his political opponents as he runs for Los Angeles mayor ... they did it in song form, ...

Chris Brown had some ... choice words for haters after Pitchfork gave his new album an awful review -- and even shaded Zara Larsson in the process. Check out his heated Insta Story ...