Sounds of contemporary bluegrass and the suspiciously heavy scent of an organic substance filled the Orpheum Theatre Thursday night as bluegrass jammers Yonder Mountain String Band played enthusiastically to a packed house. Their combination of guitar, banjo, mandolin and bass created both traditional bluegrass and incredibly fast licks, adding a country twang and a slightly heavier rock-and-roll nuance to their music.

Yonder Mountain String Band was formed in 1998 after mandolinist Jeff Austin and banjoist Dave Johnston met in college and moved to Colorado to soak up the mountain vibes. There, the two met bassist Ben Kaufmann and guitarist Adam Aijala and started touring as the Yonder Mountain String Band. The group has recorded four live albums and four studio albums since 1999; their most recent studio album, the eponymously titled Yonder Mountain String Band, was released in 2006. The band also tours extensively, including gigs at nationally-known festivals such as Telluride and Summer Camp.

Since their formation in 1998, Yonder Mountain String Band has developed somewhat of a cult following on their heavy tour circuit. On Thursday night, fans included mostly dreadlocked twenty-somethings and an older dynamic trying to appreciate the traditional bluegrass aspect of the show. Clouds of smoke rose from the undulating sea of audience members in front of the stage as older couples strained to see the band despite all the dancing in the aisles. Several attended the show in costume, including someone dressed as a banana who had reportedly given the band a six-pack earlier in the day.

The three-and-a-half hour set included traditional bluegrass songs as well as more contemporary string-picking, solos and grooves. The show opened with "On The Run," a song with a classic country twang about a man on the run "because he just slept with Annie and she’s the sheriff’s wife." The song’s playful nature allowed for improvisational breakdowns that showcased each musician’s skills on the strings.

Several more traditional bluegrass songs followed, accompanied by a light show that created a pyschedelic ambience. Bassist Ben Kaufmann introduced the upbeat "Rag Mama," on which he contributed vocals. Kaufmann’s deviation from standard bluegrass chord progressions into heavier bass grooves was a definite highlight of the set. However, energetic, head-banging mandolinist Jeff Austin stole the show, strumming the instrument’s eight strings with the fervor of a heavy metal guitarist.

A moody, foreboding jam was followed by what Austin described as "the saddest song in the history of bluegrass," "Children Are Crying." According to Austin, "If you survived this song without shedding a tear, you have a heart of stone."

"New Horizons" was next, on which the band started out slow and gradually increased the tension, as Kaufmann played bass with a bow instead of picking. The song seemed to disappear into a soulful, strained jam while the chorus did not return until several minutes later.

After a brief intermission, Austin took the chance to rock out on the mandolin while guitarist Adam Aijala played electric guitar and used disortion and feedback. Several impressive guitar and banjo solos added to the second half of the set, when songs included "High On A Hilltop" and "No Expectations."

Yonder Mountain String Band seemed to play without a definite setlist, relying on audience reactions to determine their set. They took requests from the audience during their encore, for which they played "Bloody Mary Morning."

A standout musical performance from each band member of Yonder Mountain String Band proved the intensity of the sound that can be created by these four great instrumentalists. Although their progressive, modern bluegrass style appeals to a younger audience, the band is still capable of making traditional and accessible bluegrass music. Yonder Mountain String Band’s passionate and excited string-picking and comical stage antics provided an entertaining concert-going experience.