There are plenty of hidden gems at the Twin Cities Jazz Festival, especially now that TCJF has wisely decided to maximize the participation of clubs along the light rail line on University Avenue. More venues than ever are participating and yet nearly every one boasts a worthwhile act or two each night — showcasing the depth of our local jazz scene. Check the complete schedule at www.hotsummerjazz.com/schedule.

Jam sessions are always a source of serendipitous magic, legend and reputation-building for any jazz confab. The new Vieux Carre in the old Artists’ Quarter space in the Hamm Building will have pianist Jon Weber hosting late night jams, re-creating the vintage TCJF at AQ nights of yore. There also will be late night “Smooth and Groove Jam Sessions” at Bedlam Lowertown for patrons and players who tilt in that direction. Both jams begin at 10:30 p.m. and run through Saturday.

Despite all that, and even with Dr. John invading the new CHS Stadium for a free Saturday afternoon concert, the best of the fest is still most likely to occur at the prettiest locale — under and amid the dappled shade of the trees in Lowertown’s Mears Park. For TCJF 2015, the organizers are offering a collection of headliners that may be the strongest since the event began in 1999. They include some big names who rarely if ever come together in the same ensemble, plus a band of young titans suddenly riding a wave of creative synergy and critical acclaim. Here are three choice gigs in the park, free of charge.

Potter/Holland/Loueke/Harland

The nexus of this phenomenal supergroup is bassist Dave Holland, a generous yet commanding bandleader who has featured tenor saxophonist Chris Potter in his diaphanous quintet and drummer Eric Harland in his jazz-rock ensemble Prism. Add in monstrously talented Beninese guitarist Lionel Loueke and you’ve got a group that can reign imperially in most any mood or tempo. Their Mears Park appearance will mark the quartet’s third-ever gig together, and first in the United States. Given the shared talent and temperaments involved, a thrilling, substantive performance seems a near-certainty. (8:30 p.m. Friday)

Marquis Hill Blacktet

Hill won the Thelonious Monk International Trumpet Competition last year, one of the most reliable harbingers of auspicious young players capable of ascending into their own distinctive style and sound. His Blacktet is a formidable quintet that keeps Chicago’s robust tradition of jazz innovation aflame. All five appear on drummer Makaya McCraven’s glorious new album of improvisations, “In the Moment.” Nate Chinen of the New York Times caught the Blacktet (which includes Christopher McBride on alto saxophone, Joshua Ramos on bass and Justin Thomas on vibes in addition to Hill and McCraven) at a gig last February and gushed words like “impeccable,” “virtuoso,” “earthy intensity” and “endlessly compelling” to describe various members of the group. They sound like an update of Art Blakey’s Jazz Messengers, coated in liquid silver. (6 p.m. Sat.)

Francisco Mela’s Crash Trio with special guest Nicholas Payton

Only Mela — a Cuban drummer with a sly yet robust approach to rhythm, best known for his association with saxophonist Joe Lovano — returns from the version of Crash Trio that performed at last year’s rainy TCJF. The group will miss dynamic tenor saxophonist Melissa Aldana. But bassist Gerald Cannon and pianist Leo Genovese have long distinguished themselves with Roy Hargrove and Esperanza Spalding, respectively. And nabbing Nicholas Payton — part of a great line of New Orleans trumpeters, whose brawny tone is as comfortable emitting funky fatback as bristling hard bop — makes for a majestic cherry on top. (8:30 p.m. Sat.)