If I remember my bands, correctly, the Doors didn’t have a bass player at all; their keyboardist simply played a bassline with his left hand.
Okay, I am not a musical historian. I play three instruments, I compose and arrange tunes, and I get into this sort of stuff. However, this is an off-the-cuff answer and not the result of diligent research.
If I had to characterize the various eras of music, I’d say that the 50s could be defined by the popularization of the electric guitar, which was then primarily used as a backbeat; close harmonic formations vocals in counterpoint to the lead melody; use of horns as a soloist instrument; piano in the rhythm section; simple drum kit; and maybe the Hammond organ with Leslie rotary speaker. The recording medium was in monophone, and the speakers were small, so there wasn’t a great need for beefy electric bass or chest-rattling toms in the drummer’s kit. Most of the music of the 50s and early 60s I can think of doubles the bass into a vocal, a piano, or a standard guitar (a more tenor sound so the speaker cone can replicate it). Because of those tiny, tinny speakers, the dynamic range of the mix was fairly compressed into a narrow treble bandwidth designed to sound best on AM radio. Structurally, the songs changed chords at the beginning of the measure, and the cadence of the melody was sometimes syncopated (that is, the emphasis did not always fall, or the note begin, on the beat). Compare the regular rhythm of Bill Haley and the Comets “Rock Around the Clock” with Elvis and his syncopated “Hound Dog.”
(To define close harmony: you don’t skip over a note in the harmony. If a C chord can be made of C, E and G, then close harmony might be C then E then G. Open harmony might be C, skip E, G, skip C, E.)
In the 60s the electric guitar began to take leads, as people figured out new ways to make it talk (cf Chuck Berry and those twangy minor thirds he used to bang out). This involved technical advances like reverb, distortion, delay, and chorus effects; and adopting some more snappy harmonies like the added 6ths, 7ths to the tonic (the main chord of the key you’re in). Electronic synthesizers were still pretty primitive until the end of the 60s, but electric pianos were coming into use. As recording technology improved, it became possible to add more and more layers to the mix, adding strings and other acoustic instruments like flute. With better speaker technology, too, you started to get more bass, more toms for the drum kit, and overall you could produce a more dense song. Think Phil Spector. Syncopation continues to flourish (as it has pretty much since ragtime). Vocal harmonies sometimes included group singing (think the Mamas the Papas, the Beach Boys) instead of bop-sh-bop stuff.
The 70s saw the explosion of the Moog and ARP synthesizers and the rise of electronic drums. (Starting with The Who and their aborted Lifetouch album.) It also saw the evolution of the power chord: the root C and the fifth G without the meddling third, the E (which sounded muddy when run through a distortion box). With the advent of stereo recording, even higher-fidelity tape on which to record, and better-quality speakers, it was now possible to preserve the high end treble and the low-end bass better than before, and since it was possible to separate sounds in the stereo spectrum you could fit in a lot more distinct instrument sounds. I think the rock recordings of the 70s are much more spare in their use of instruments than previously; but we also have the pop/disco fragment that said “more is more” and filled the stereo space with as much as possible. With more instruments, we started to see a lot more rhythmic counterpoint and mid-measure chord changes. A few bands (such as Foreigner) began to do more with suspended fours and twos. (That is, CFG or CDG, instead of CEG.) We also began to see more duet solos (in thirds, ala Brian May of Queen) and doubled vocals (in thirds, not exactly a new invention) instead of the wah-wah-doo-wah-doo of the 50s. Keyboards played mostly a solo role against the rhythm section of guitar, bass, drums and sometimes piano.
Now we come to the 1980s. Digital recording was pioneered around this time; Billy Joel’s The Nylon Curtain of 1981 was digitally recorded. The fidelity of recording was higher than ever, and digital sampling enabled keyboards to more accurately replicate the sound of real instuments. MIDI solidified itself in the marketplace. Moreover, the market was becoming crowded with new, wholly synthesized digital instrument sounds. Programmable rhythms became possible, to repeat the same backbeat while the soloists performed. As a backlash against the Moogs and ARPs, some musicians turned to that fat horn sound again (such as the Tower of Power horns section, or Mussel Shores, et al). Acoustic instuments became solo instruments against the keyboard backbeat, reversing positions from the previous decade.
Somebody else can tackle the 1990s if they want. Me, I’d start the analysis with the subwoofer.
I stress that these are all just personal observations made up off the top of my head, and may in fact be completely subjective and/or a bunch of lies, depending on a) when you graduated from high school and b) what kind of music you listened to. 
FISH