On occasion, he would be seated at the piano, already tinkling the introductory notes of a song, when a request shouted from the crowd would cause him to pop up and grab a guitar in order to oblige. These solo sets almost always include a core inventory of hits sprinkled throughout a two-and-a-half hour showcase, but once in awhile Browne will venture off into the depths of his collection with unpredictable spontaneity.

This happened twice during the UPAC show.

The first hilarious surprise came about a half-dozen numbers in, when someone roared for "Free Bird." Apparently, Browne had heard this once too often and decided, if you can't beat them, join them. With that, he launched into a full-length cover of the seminal Lynyrd Skynyrd ballad, complete with a spot-on slide solo courtesy of his guitar tech, who wailed the familiar hook from the wings on a brilliant white Stratocaster.

The second equally amusing incident came when Browne basically stopped performing "Alive in The World" mid-song because he forgot the lyrics, and called for someone off stage to print them up. While that was being done, Browne ventured back to his debut for "Looking Into You." Then the aforementioned lyrics were delivered, and his do-over commenced--with a few momentary stops as he squinted at his cheat sheet.

Browne didn't dwell too long on "Time the Conqueror," but the intermittent samples from that project stood strong beside his most popular and endearing creations. "Live Nude Cabaret" and "Going Down to Cuba" were particularly well received and interesting to hear in contrast to the arrangements of those numbers with the full band where instrumentation overshadowed the lyrical content by default.

This is one of the reasons why attending at least one of these solo Jackson Browne shows is an absolute must for fans. While the full-band shows provide the full instrumentation they are used to hearing on the record, these solo shows shift the burden to Browne's lyrics and vocal delivery.

On his first switch from guitar to keyboard, Browne honored a request for "Sky Blue and Black," plaintively sketching the story out on a stark and nearly empty background of just a few piano chords. Selections like this gave the audience an opportunity to really hang on every word, as did his renditions of "For A Dancer," "Late for the Sky" and the incredible "Sleep's Dark & Silent Gate."

As counterpoint to the more sad or introspective piano tunes, Browne chose from among the 16 various guitars he brought along for just such an occasion, pulling out a plucky two-step beat for "These Days," and a sizzling politically-charged "For America" to close out his first set.

He also got the crowd on its feet a little later with up-tempo takes of "Running on Empty," "Doctor My Eyes" and "Somebody's Baby." And, before launching into "Rock Me On The Water," Browne took a few moments to rally the audience around his latest cause: reducing the use of plastic beverage containers.

The artist said he typically avoids hawking product during his shows, but asked folks to consider purchasing a stainless steel water bottle from the concession stand to help save the environment. According to Browne, only about 15 percent of all the world's plastic water bottles are recycled, and most of those are eventually shipped to China and incinerated, causing equally harmful atmospheric pollution.

The rest, he said, end up in landfills where they leech chemicals that, ironically, poison the natural water tables below. He also drew attention to the Great Pacific Garbage Patch, a vortex of plastic bottles and similar junk that has turned a piece of the Pacific twice the size of Texas into a murky goo that is poisoning fish and upsetting the entire world's ecosystem.

Despite measured doses of political activism that occasionally overshadow his musical contributions, the show wrapped with what has become a standard show closer and affirmation for Browne: a cover of "Little Steven" Van Zandt's "I Am A Patriot."

Browne continues the current leg of his solo tour through Dec. 7 before he breaks to prep for a package of co-headlining shows with Sheryl Crow in Japan in March 2010.