Popular music has rewarded such improvisation-based acts as the Grateful Dead and, more recently, Phish and Widespread Panic, as well as a host of imitators.

But today, bands that focus on improvisation face the twin challenges of mastering one of the most daunting aspects of music while also finding ways to stand out from the pack.

Three bands performing at the 40 Watt tonight – The Heavy Pets, The Mantras and Laissez Funk – do their best to overcome these obstacles.

“We definitely see ourselves in sort of the jam scene, but we want to break out of that and make it something new,” said Bill Bacon, drummer for Athens-based Laissez Funk. “We don’t want to necessarily follow in the light of [Perpetual] Groove or Widespread Panic.”

Laissez Funk will open for The Heavy Pets, whose show in Athens is part of an extensive touring schedule this year.

A September tour ended at the Pet Zoo! Festival in Pennsylvania, the 40 Watt show falls at the tail end of a short Southeastern tour, and October will see the Heavy Pets play 10 shows in as many days with Massachusetts band The Brew.

“We’ve done 10 nights in a row before, but not since summer 2006,” guitarist Jeff Lloyd said. “I wouldn’t wish it to anyone.”

Although The Heavy Pets focus on improvisation and jamming, it nonetheless maintains professionalism and structure in its live performances.

“We rehearse constantly. . We’ll have certain riffs or tags that we’ll go back to to indicate that this is the end of the tune,” Lloyd said. “It’s jamming but there’s a lot of structure to the jamming itself.”

Newitt’s role as drummer and rhythm keeper in these jam sessions is particularly important. “You have to keep things interesting but not be too crazy all the time,” he said.

The band will be entering the studio to begin work on a new album after Thanksgiving with a new bass player, Justin Carney.

Supporting act The Mantras, from Greensboro, N.C., describes itself as a rock, funk and jam fusion band.

After winning studio time at Floyd Fest in southern Virginia, the band will begin work on its third studio album in November.

Guitarist Keith Allen emphasized some major differences from the group’s past body of work.

“The first couple of albums were mainly focused on stuff that had [already] been written and then we worked on in the band. The new album will focus on stuff that we’ve written as a band,” Allen said. “It has more of a Mantras staple sound.”

Although the group doesn’t try to dissociate itself from the jam scene, it has a distinctively heavier approach to improvisation than most of its peers.

“When we play and when we improvise, there’s a certain type of urgency behind the music,” Allen said.

“A lot of bands with the jam band moniker can be a little bit too mellow, or too laid back, or too pretty at times.”