It’s been a rough year or so for trumpeter Malachi Thompson, but battling for his life against major disease has toughened his outlook and stripped from his music the gratuitous incidentals that used to prove such major distractions. These days, even when the flesh weakens–that is, when his energies flag and his lip falters–the spirit is high, and in jazz, that counts for a lot. So does the Freebop Band, which strikes a balance between bebop (the fundament of modern jazz) and the wilder offshoots of the music’s avant-garde. What’s more, the band sports one of the great tenor players of the last two decades, force of nature Billy Harper, who combines the Texas tenor tradition with the expressionistic power of John Coltrane to create a timeless, potent stylistic vehicle. Harper’s last visit to Chicago–with Thompson, nearly a year ago–was his first in about a decade, and it was immediately cclear that he hadn’t lost a step, or any of the spiritual drive that distinguishes his work. Listening to Billy Harper is still like standing in the middle of a hurricane: a haven of serenity surrounded by something akin to pure energy. Tonight and Saturday, the Bulls, 1916 N. Lincoln Park West; 337-3000.