Hello there,
I think I can give you a much different perspective than the other answers. I was alive and listening to rock back then and even before Jimi (yep, I am that old). I started playing guitar in 1957, so I probably listened to music differently than most others at the time. They listened to see if they liked the music in general. I studied how the guitar player played and what he did. And I have the pleasure of watching Jimi play. He was amazing.
No, music was not all vocals back then. Heck, Dick Dale and Link Wray paved the way for a driving guitar sound. Link Wray was the great grandfather of distortion. Dick Dale was the King of Loud. And in response to those who think the instrument was not important, I guess they have never heard Nokie Edwards, Jeff Beck, Eric Clapton, Jimmy Page, or John Mayall.
Jimi was a hard working, gigging musician. He honed his craft working the Chitlin circuit. Nothing really like that these days, but that was a hard road. There were idiosyncrasies to Jimi's playing style and set up. Those were not accidental. He was fully aware of the tonal differences in what he was doing.
There were many good guitarists in the 50s and early to mid 60s. For ever one of those I named, I could have named 5 others. But Jimi was truly unique. He did things with a guitar I never dreamed of. Just watching him always blew my mind. Sure I am a nobody guitarist, but Jimi's fans were not all no-names. Paul McCartney, John Lennon, George Harrison and Eric Clapton were all big fans of Jimi long before he became the famous guitar icon. Two of those fans, Paul McCartney and George Harrison, had a major hand in Jimi's break through here in the US. They were organizers of the Monterrey Pop Festival (even though the Beatles could not play due to contract problems) and they arranged for Jimi to be included on the program. The rest is history.Jimi's historic performance at Monterrey was the spring board to his fame in the US.
Yes he was different from other guitarists. That is why so many guitarists of that period (and budding guitarists like Joe Satriani) were such big fans.
How did he change the face of music? He did, but it is hard to put into words. Friends used to think I was weird for listening to some left handed guy play blues on a right handed electric guitar turned upside down with strange distortion that ended up sounding like something from an acid trip (the term acid rock was not yet used, nor was psychedelic). Then after the movie about Woodstock came out in the theaters in 1970, I had all those folks coming to me saying I needed to check out this great new guitarist they had discovered. Yep, that same left handed blues guitarist, Jimi Hendrix. What was the difference? About 4 years. In that span of time, youth culture had fully embraced the hippie movement, acid rock was now a term, psychedelic this and that was all the vogue. And not that culture had a poster boy. A face for all to identify with. But that was all fluff. If there had been no real substance to Jimi's playing, he would be as well remembered by today's youth as Link Wray. Most artists are sponges. They (we) absorb all sorts of influences from life and interpret those and incorporate those influences into their art. Sure, Jimi did that, just like anyone else. But there was something new and something different about how Jimi presented that. That made what he did stick with other guitarists. He became the influence on their work and was incorporated into their art. Every time I overdrive my amp to get that sweet harmonic feedback, every thing I play an inverted chord, or do a wild slide, I am in my own way paying tribute to one of the finest and most unique guitarists every. But then I saw him play and he blew my mind.
And even with all the progress in playing styles and how the boundaries have been pushed ever so much father than 1969, when I hear certain techniques I remember Jimi did that. It still blows my mind.
Later,
Hello again,
Jimi did get a lot of guidance and tips from other blues and R&B players along the way. Curtis Mayfield and Steve Cropper were two. But his big influence was Little Richard. When Jimi was playing guitar in Little Richard's back up band, he decided he wanted to make his guitar do what Little Richard did with his voice.