FORT WORTH — Like a band breaking up before fans are ready, the Fort Worth Symphony Orchestra signed off on another Concerts in the Garden season Saturday night in front of a packed audience at the Botanic Garden. The farewell performance welcomed a British invasion, of sorts, the day after America celebrated its independence; Beatles tribute band Classical Mystery Tour, under the direction of guest conductor Martin Herman, joined the orchestra.The music: Herman, an accomplished composer and arranger, wrote the orchestral transcriptions for the Classical Mystery Tour show, and the fast-paced concert included about two dozen of them. The fab four tribute artists — Chris Camilleri, David John, Jim Owen and Tony Kishman — played instruments and lent groovy British accents to all the crowd favorites from I Wanna Hold Your Hand to Sgt. Pepper’s Lonely Hearts Club Band to Come Together. They wore a few different costumes as the night went on, too. A particularly nice moment came toward the end, when Give Peace a Chance segued into a lovely piano introduction of Imagine that swelled to lush orchestra fullness onstage and a sea of cellphone “lighters” waving in the crowd. The mood: Nostalgic and as surprisingly mellow as the temperature on the breezy July night. While kiddos played with psychedelic light-up hula hoops, wands and swords, their parents belted out the choruses to the popular songs (“We all live in a yellow submarine …”) and grandparents sang every note. The audience skewed heavily toward grown-up baby boomer Beatle-maniacs. Memorable moments: The concert brought the skies above Fort Worth one last blast of fireworks in a week of many. Also, at intermission, a lucky patron named Richard won a Cadillac in a season-long raffle that raised more than $65,000 for the symphony’s many outreach and educational programs, organizers said.