Thirty years strong, its evolving ranks still fronted by horn veterans Tom Halter, Charlie Kohlhase and leader Russ Gershon, local treasure the Either/Orchestra makes a rare stop at the Regattabar on Friday for a night spanning modern jazz originals, an Ethiopian traditional song and a cameo by singer Gabrielle Agachiko. The same night, Blackberry Smoke brings its jamming blues and country-tinged brand of classic rock to House of Blues, while the Nile Project brings musicians from 11 African countries together for a hypnotic mash of instruments and cultures at Boston University’s Tsai Performance Center, presented by World Music/CRASHarts.

Free-jazz enthusiastists have a treat in store Friday through Sunday at the first Brandeis Improv Festival, which takes over that Waltham campus with interesting programs that are free and open to the public, including performances by drummer Milford Graves, pianist Tim Ray, guitarist Dave Tronzo and the collective Club d’elf. Here’s the full rundown.On Saturday, in another World Music/CRASHarts show, the nine-piece Heritage Blues Orchestra bridges blues, jazz and gospel from the country to the urban landscape at the Somerville Theatre. Shoegaze rockers Swervedriver crank up the guitars once again at the Sinclair. But Saturday’s most eye-catching bill pairs the gritty, impressionistic Texas singer/songwriter Shakey Graves (pictured) and sassy, eclectic country singer Nikki Lane — whose All or Nothin’ remains one of my favorite 2014 albums – in an early show at Royale.

Sunday, however, may offer the most potential for surprise. The coy, charming Texas chanteuse Kat Edmonson shares her unique voice at Scullers Jazz Club, for a 4 p.m. matinee as well as an evening show. Tabla virtuoso Zakir Hussain brings his Celtic Connections ensemble to the Somerville Theatre in a third program by World Music/CRASHarts. And the under-the-radar indie supergroup Diamond Rugs, including Deer Tick’s John McCauley and Los Lobos’ Steve Berlin, stokes its swinging party tunes at the Sinclair to cap the weekend.