In this reprinted piece from Popular Mechanics, 2015, the late, great Eddie Van Halen talks about how he modified his early guitars and amps to help create the unique guitar sounds for which he became famous.
My playing style really grew from the fact that I couldn't afford a distortion pedal. I had to try to squeeze those sounds out of my guitar. The first real work I did was in my bedroom. I added pickups, because I didn't like the sound of the originals.
Most guitar necks are too round on the back, so I took sandpaper and reshaped the neck to be very flat. I actually refretted a few guitars early on because I wanted to shave the fingerboard down and make the neck even flatter. The flatter it was, the farther I could bend a string without fretting out, or choking the sound when the string hits a fret higher on the neck.
My first real guitar was a Les Paul Goldtop. I was a total Eric Clapton freak, and I saw old pictures of him playing a Les Paul. Except his had humbucking pickups, and mine had the soapbar, P-90 single coils. The first thing I did with that guitar was chisel it out in the back and put a humbucker in. When we were playing gigs, people kept saying, "How is he getting that sound out of single—coil soapbar pickups?" Since my hand was covering the humbucker, they never realized that I'd put it in.
Read the rest here.