Equal temperament, where all the keys have basically the same intervals rather than having different characters as in just intonation. Enabled modulation from one key to another as in Bach and Jazz.

This is maybe obscure but Earl Scruggs basically invented three finger picking on the banjo. It became one of the defining characteristics of bluegrass music and when most people imagine “banjo music” today, that’s probably what they imagine first. (It’s called “Scruggs Style” and he popularized but who knows who did it first as a lark?)

A recent one is abusing autotune. Autotune was invented to correct singing notes that were slightly off. Cher was apparently first to do this but people started experimenting with unintended settings combinations to make different effects and stuff. T-Pain took that to the extreme and it became a whole trend in pop music.

Plus, like, the entire history of music in New Orleans and the surrounding Mississippi Delta region. So much American (and British) music can trace a direct line to the blues, jazz, early rock and roll, and other genres that begin in the region.

• Jamaican dub. The concept of the engineer as artist and producer and also the idea of remixing comes from dub, which was invented by people like King Tubby and Lee Scratch Perry. The way most modern genres are produced (by a creative audio engineer, without a band) originated from dub.

There have been lots of technological advancements which led to revolutions in music. The electric guitar, multi-track mixing, synthesizers, etc.

Each of them brought with them while new genres of music.

So many great examples in this thread already, so I'm going to go with a simpler one: Guitar overdrive. intentionally increasing the gain beyond max input level of the amplifier to produce a more square wave tone would've seemed sacrilege to guitarists from the 30's and 40's.
And today it's the foundation of so many guitar sounds and music genres.

Dave Davies of The Kinks changed rock music with a razor blade. Distortion pedals existed but they couldn't provide the same kind of fuss sound that we hear in "You Really Got Me"... but a year later they could.

Probably when some people started using the studio as an "instrument", like Phil Spector with his Wall of Sound, or Brian Wilson of The Beach Boys during the Pet Sounds sessions. Never before had music sounded so good and rich in sound.

Van Halen finger tapping the fretboard. Didn't last as a trend, but every guitar player tried it at the time.

Les Claypool from Primus playing lead bass. That was so unique, I don't think anyone really copied it. A watershed moment anyway.

Neil Pert YYZ or the solo from Tom Sawyer. Same reaction from drummers as guitarists for Van Halen. Blew everyone's mind as to what was possible by one drummer.

Obviously there was nothing like Jimmy Hendrix either, but there was so much new and experimental music at the time he unfortunately gets lumped into "60's music" IMO.

The MC5's performance at the Chicago DNC in 1968 (and by extension Punk Rock). "Kick out the Jams, MOTHERFUCKERS!"

Hendrix. Hendrix is the fosbury of music. Dude went off in his own direction in both technical and compositional terms, and a lot of people followed.

There's solid points in the comments, but I feel like we're talking about a single individual ignoring convention here, and there's really only one answer in that context :)

The I–V–vi–IV progression

https://en.m.wikipedia.org/wiki/I%E2%80%93V%E2%80%93vi%E2%80%93IV_progression

Dubstep... It's all about that drop.

/s

Not just one imho: if we go that back in time I'd start with electric instruments, more recently (~50 yrs ago) multitrack, then electronic music (whether you have it started with synth in the 80s or with music entirely made on a computer in the early 00s). All 3 changed the game and were adopted by everyone

The Amen break is sampled absolutely everywhere in modern music, that's probably the closest you'll get to absolute ubiquity like the Fosbury flop

For guitar :

two handed tapping

sweep picking.

I don’t believe music was ever considered done and perfected but I’ll throw in looping. What single musicians are able to do with this technique is amazing. But not sure who invented it.

I would say going from analogue to digital recording. Digital made edits possible that where impossible before.

Ice-T's Original Gangster

Absolutely changed the course of rap history. In a good or a bad way is up to you, but O.G. was the O.G.

I go with autotune. Biggest change in the last 20 years and everbody is doing it from amateur to professional.