Fans who saw ZZ Top during their recent tour stop in Huntsville, Ala. witnessed an unusual sight, as bassist Elwood Francis briefly performed using an oversized 17-string bass.

The mammoth instrument wasn’t just a prop. Francis proved it could actually be played by using the bass for ZZ Top’s first number of the night, the 1983 Eliminator tune “Got Me Under Pressure.” In fan-shot video (see below) the bassist can be seen strumming along on the comically large device, much to the delight of frontman Billy Gibbons.

No explanation was initially given for the giant instrument, as Francis moved to a more traditional bass for the rest of the concert.

As it turns out, the behemoth bass was actually the result of some late-night web browsing. Yes, ZZ Top discovered their newest instrument in the same way that average people end up buying weird gadgets and gizmos on Amazon.

“I was doing night internet searching [and] turned up a picture of this crazy 17 string bass,” Francis explained in response to an inquiry from UCR. “I sent a picture to Billy and we laughed about it and made some jokes about actually trying to use it.”

The story could have ended there… but where’s the fun in that?

“A few weeks later, after I had forgotten about it, Billy shows up with [the 17 string bass],” Francis explained, describing the situation as “one of those ‘hold my beer’ moments.”

Francis joined the ZZ Top last following the death of bassist Dusty Hill. Since then, the musician, who had served as the group’s longtime guitar tech, has been a natural fit in the trio.

“He’s adding a great bit of enthusiasm,” Hill remarked in July. “When I see [drummer] Frank Beard smiling for the first time in 30 years, I know something good’s happening.”

ZZ Top is in the final days of their Raw Whiskey tour, ending Dec. 2 in Scottsdale, Ariz. From there, the group heads to Las Vegas for a residency at The Venetian Resort and Casino. No word as to whether the 17-string bass will be making a return appearance.