Wishbone Ash may not have invented the twin-guitar attack in rock music, but the British prog-rock band was there from the technique’s early days.

In the United States, the Allman Brothers and Lynyrd Skynyrd famously showcased twin-guitar leads. Andy Powell, the one continuous member of Wishbone Ash, believes Wishbone Ash and the Allmans developed twin-guitar leads in tandem. “In the U.S., the Allman Brothers had a Sou...