Broadly speaking, we can divide musicians into formally trained musicians who play from standard notation as with a string quartet or symphony musician, and the rest, who can be called folk musicians. I'm one of the latter. I learned how to read standard notation, but it's not how I notated songs when I was figuring them out from recordings, and not what the song sheets that I gave other musicians in the band to play from.
Folk musicians include rock, blues, country, bluegrass, and more.
Plus, formal musicians don't generally improvise. A trained pianist plays only the chords and melodies as written, whereas the Grateful Dead's keyboardist wasn't looking at anything written and played every version of any given song at least slightly differently.
But yes, Hendrix was one of a kind. His music still sounds fresh and modern today. Nobody needs to re-record All Along The Watchtower (a Dylan song) although many have, including one of my favorite bands, The Grateful Dead, but not as well in my opinion. "Let us not talk falsely now. The hour is getting late."
Have you ever seen tablature, or just tab? On the top is standard notation. It's for any instrument that can play chords (on the left) or a melody (on the right), but the bottom notation is only for guitar. Standard notation is on five lined staffs where lines and spaces stand for notes modified by the sharps and flats in the key signature, but the tab is on a six-lined "staff" which represent the six strings of a guitar, and tells you which fret to put a finger on. Standard notation also provides a time signature, and the notes indicate how much of a measure they should occupy.
Like I said, I read both, both never use the standard for anything. The design on the left tells you that this is a treble clef, and that the lines stand for EGBDF, or every good boy deserves favor as many have learned it. The two sharp signs tell us that F's (the top line of the staff) and C's (the second space) are all sharped, and that this music is in the key of D major, which diatonic scale (do-re-mi) goes D-E-F#-G-A-B-C#-D.
The C means common time, or 4/4 time (ONE-two-three-four, ONE-two-three-four), tells us that each measure has four beats, and that a quarter note is worth one unit of a beat.
But the guitarist doesn't need any of that except to know where to put his fingers on the neck and how much music goes into each measure if he knows the song. If he doesn't, he listens to a recording until he does, then looks at the tab. That's folk music.
There's an even simpler way of notating songs than tab (below). These are the chords and lyrics to Elizabeth Cotton's Babe It Ain't No Lie, which I learned listening to the Dead, and which our band covered. If you listen along, you'll note that each verse is played a little differently - same chords, but picked according to whim - and also, you'll see how the lyrics in folk songs evolve. These are not the exact same words I'm singing. I guess I heard them wrong, but that's how it goes when one takes the music from a recording instead of paper, which just wasn't available when I was figuring these songs out.
If you're interested, try to follow the chord changes while looking at the chord names and pattern. This was a live performance, and my wife is signing harmony in the choruses. It begins with an instrumental verse. The only improvisation here comes in the final instrumental verse, and also a few passing chords I added:
Intro:
C F C F G C C F C F G C
G C E E7 F F C D C G C
C F
Been all around this whole round world
C F G C
And I just got back - today
C F
Work all the week, honey I’d give all to you
C F G C
Honey, babe, what more can I do?
G C
Oh, babe, it ain’t no lie
E E7 F
Oh, babe, it ain’t no lie
F C
Oh, babe, it ain’t no lie
D C G C
You know this life I’m livin’ is mighty fine
C F C F G C C F C F G C
G C E E7 F F C D C G C
C F
One old woman, Lord, in this town
C F G C
Keep-a tellin’ her lies on me
C F
Wish to my soul that old woman would die
C F G C (walk down C to G)
Keep-a tellin’ her lies on me
G C
Oh, babe, it ain’t no lie
E E7 F
Oh, babe, it ain’t no lie
F C
Oh, babe, it ain’t no lie
D C G C
You know this life I’m livin’ is mighty fine
C F C F G C C F C F G C
G C E E7 F F C D C G C
Anecdote: When I was a young guitarist, I sat down with my sister-in-law, who was a classically trained pianist, to play together. I suggested a 12-bar blues in A (the key), which defines the chords and their progression: A-A-A-A D-D-A-A E-D-A-E. She had no idea what I was talking about. She didn't think in those terms at all. She didn't know what an A chord was, but if she saw a treble clef with three sharps (key of A major) and quarter notes stacked on one another in the top three spaces, she could play that, but didn't know to call it an A major chord. We didn't get very far. That was my first realization of how different our musical worlds were.