Here's my (temporary) breakdown of Hotel California:
Basic track: drums, bass and twelve-string rhythm (by Felder, I reckon).
Guitar overdubs:
- Another twelve-string electric (doubling the first one), most lilely by Felder although it could've also been Joe... or Glenn... but most likely Felder.
- Felder's acoustic on the second part of the intro: bass-doubling and some arpeggios. Definitely his style.
- Glenn's acoustic: strummed chords from the first chorus onwards. He double-tracked it from the fourth verse onwards.
- The reggae staccatos, which reportedly Glenn recorded at first but then Joe replaced.
- A clean Strat (or maybe Tele) doubling the bass one octave higher at some points. Most likely Felder.
- A two-part harmony playing throughout. Possibly Felder played both (Don and Joe would do it on stage for practical reasons).
- Another two-part harmony, entering on the fourth verse and playing some antiphonies with the previous one. Felder did both IMO.
- Don Felder's lead, playing some licks (e.g. on the secod chorus) and then the famous solo.
- Joe's lead, doing the second part of the solo and then harmonising with Felder's lead.
All of that means the original recording has thirteen guitars (or perhaps even more if the harmonies were double-tracked to give them a fatter sound, in which case there are seventeen guitars), of which Glenn and Joe played two each, and Felder did the rest.
There are also some keyboards: an organ and a piano, both playing softly in the background. The piano's a bit more noticeable on the first verse (just when Don sings 'hair') and on the fourth (when Don sings 'night'). I'd suppose Glenn played both, but it could've been virtually anyone in the group... most likely, whoever came up with the idea of adding them... but most likely Glenn considering his story of ever so subtly overdubbing keyboards. Those two overdubs aren't too noticeable but if you take them out the song loses some of its magic.
Despite what happened on stage, harmonies didn't include Joe or Felder at all. Choruses are Randy and Glenn (plus Don's lead of course) and the 'and still thsoe voices are calling from far away' line is just Don + Don (so yeah, they did do self-backing vocalist).