The tools for analyzing already recorded music is extremely accessible today; especially if you can find stems for the tracks you're interested in (any songs that have appeared in Rock Band or Guitar Hero have stems available if you dig a little or extract them yourself...pretty sure Rush songs have appeared in those games, and certainly something Gadd has appeared on has as well).

You could do that analysis.

Session players often seem superhuman because they've really deeply studied so many styles and genres. They're like world class athletes, in that their lives revolve around playing their instrument flawlessly and with minimal rehearsal time. Some of these famous tracks were done in just a couple of takes, and the session players might play on dozens of tracks for multiple artists in a week. Most rock bands would kill for that kind of efficiency. (And, I'd bet there are session players that'd be able to replicate Peart's style reasonable effectively.)

The documentary "Steely Dan : The Making of Aja" (available on YouTube[0]; some assembly required) has fascinating segments on how the performances were assembled.

Quoting from the Wikipedia page on the title cut[1]:

"According to (Historian) Sweet, Gadd's playing was so visually appealing to watch that some of the other players became distracted and had to rerecord portions of their parts later."

[0] https://www.youtube.com/results?search_query=steely+dan+aja+... (also has one of Gadd explaining/demonstrating his performance)

[1] https://en.wikipedia.org/wiki/Aja_(song)

Steely Dan records, Aja in particular, are what happens when you get the best session players in the world in a studio with a huge budget and guided by a couple of guys whose egos didn't get in the way. They often let the players play whatever they felt was right for the song. They understood that when you've got somebody of the caliber of Purdie at the drums, you don't really need to tell him what to play, you just get out of the way. I've always really appreciated the quality of the recording of Aja, but as an adult I've grown to love the music, too.

And, yeah, I also recommend that documentary. Several of the Classic Albums series are really good. Dark Side of the Moon and Rumours come to mind. They also happen to be studio masterpieces, often listed alongside Aja as being pinnacles of recording quality. (Interesting how they're all from the same era. That sort of big album industry was a fleeting thing.)

"And, I'd bet there are session players that'd be able to replicate Peart's style reasonable effectively"

Replicating Peart's style is hard but not impossible, though many drummers (even great ones such as Mike Portnoy) often get it wrong because they look for speed and perfect timing while the strongest point of Peart has always been his sense of dynamics: he could make a song by hitting only a single drum just by modulating strength of the hits, their speed and time changes.

Jazz musicians are picky about rock drummers invading their lawn (for very good reasons I'd say), but I think Peart made it pretty well. Check this one at the Buddy Rich Memorial Concerts and don't miss the solo, this sounds like a variation of the old solo in the Exit Stage Left live album) I like this one a lot more than the newer ones. https://www.youtube.com/watch?v=T0gYHLkY4qA

To me his very distinctive traits also are his use of upbeats (in fills too) and that famous ride pattern which totally raises attention among Rush fans as soon as you start playing it. These guys nail it well. https://www.youtube.com/watch?v=LRhTmDSrNvE https://www.youtube.com/watch?v=aYaVZojowiQ

> Peart

Prof. Moriarty of Sixty Symbols discussed[1] this paper, where he was particularly interested in extending the research into other drummers and music styles. For a while, he was asking[2] people to submit covers of the drum track for Tom Sawer for analysis.

[1] https://www.youtube.com/watch?v=GyLeBMdI_HU

[2] https://www.youtube.com/watch?v=vGH6-BcKCME