Few bands have a reputation for making music as consistently honest, organic and daring as Gov’t Mule. Now the enduring group fronted by visionary singer-guitarist Warren Haynes returns to Humboldt State University.  Gov’t Mule is known for the inventive and incendiary musical performances that spring from the jazz-like philosophy and creative language the Mule’s members have developed together. They’re the rare rock ‘n’ roll group with an improvisational heartbeat, which allows all four musicians to expand on the songs’ themes in non-formulaic ways. That quality distinguishes the finest jazz, blues and rock recordings of the ’50s and ’60s, but is largely absent in modern music.