In the 1960s, electric-guitar players were looking for something more than the twangy country sounds of the Fender Telecaster , the tremelo effects produced by a Bigsy whammy bar on a Gibson Flying V, or the reverb that was built into many amplifiers . They wanted to be able to boost their volume, distort or delay sounds, and filter their notes and chords to replicate everything from background choruses to jet airplanes. One of the first...