I think a change of title would get you better replies; I thought we were gonna brainstorm new musical instruments ITT, or discuss strange musical instruments of history.
The electric guitar as most people imagine it was around since the 1940s and a little earlier, stemming from attempts to amplify a guitar's sound in the early 20th century. To popularize the new sound in music genres earlier, you'll have to fiddle (no pun intended) with culture a bit to find some way to gain mass acceptance. A countercultural movement probably wouldn't work in the 1940s we know, so unless there's a cause for anti-government sentiment in this era you can't just repeat Woodstock.