Port Arthur’s most famous living musician returns for his first album in five years, and it’s an opportunity for a host of rappers to pay homage. Big K.R.I.T. produces the strongest track, “Outta Season,” which is the soulful, bluesy equivalent of riding on dubs with the top down, the breeze floating through your hair. Yo Gotti and 2 Chainz guest on “Traphandz,” which sounds more like circa-2005 trap than its current Metro Boomin-led variant. Gary Clark Jr. and Leon Bridges help Bun B pay homage to his late UGK partner Pimp C on the electric-blues elegy “Gone Away,” and the voice of Pimp C turns up on “U Bitch.” With so many guests — Run the Jewels, Lil Wayne, and UK rapper Giggs also appear — Return of the Trill is less an opportunity for Bun to flaunt his skills than a chance to throw a chain-swanging Texas party, with himself at the center of it. Then again, as a Promethean figure in Southern hip-hop, he doesn’t have anything left to prove.