The reverb wanders off to one side a bit but it's a distorted guitar and a distorted bass which is clearly your intent. For what it's worth I just think the basic premise is the issue here. The music doesn't support the techniques and treatment. Vivaldi and Bach tend to turn into 80s TV game music when this is done. The great bass player Herbie Flowers experimented with an album of electric bass and classical style guitar and suffered the same problem, the blend of tones just doesn't work. This is the snag here. I've never used two eqs to do what you have done, so I kind of wonder if everything you are doing is basically for effect, not for conventional polishing and honing? Walter/Wendy Carlos switched on Bach come to mind.
It's not bad in every individual department. The odd way of doing EQ seems to have worked. The reverb on the bass and it's distortion and EQ sort of work, it's that the sum of the parts is just not, in my humble view, easy to listen to. Instead of being nice to listen to, it isn't. He concept. The snag with these kind of experiments, is the audience. A typical Vivaldi audience will hate it. A Mandolin lover will hate it, a typical metal head will hate it. Not because of your musicianship, or your recording techniques, which despite being a little er, unusual, have worked ok. You have created a new product, a new genre and I jus don't know who will be your listeners. I listened to the end as that's what we do here isn't it. Liking music isn't the point, but I was left with the impression most searchers who find it would press play and click away very, very quickly. It's such a strange combination - distorted Vivaldi and I'm not sure we can comment properly because we have nothing to compare it to? Personally I even find it difficult to comment on recording quality because with all things distorted the purity of the sound sources is compromised on purpose. As you say, it leaves you with eq, distortion and reverbs and delays that kind of thing, but these choices conventionally need a genre to latch on to to enable comment and consideration. The only distorted guitar success on old music styles I can think of was Jeff Beck who found some music styles that worked together. I'm left wondering if the music wrecked the success here. It's clever, it's complex, but very difficult to listen to I am afraid.
I had a listen to the stems and there's one other thing that gets in the way. dynamics - there aren't any because of the distortion - especially on the bass. So in the violin part you would have normally BUM-di-di-di, or DI-DI-bum-DI-DI, but your version just goes BUM-DI-DI-DI, or DI-DI-BUM-DI-DI and it conventional distorted guitar music, the best you'd get would be palm muting to dull the lowers, or the edge of the pick to add harmonics on certain notes, and with Vivaldi fast and furious you cannot do this so you cannot do the dynamics properly - not because of recording or even playing technique, but simply because style clashes with techniques.
One thing is that you have to work very hard to hear more than two instruments - guitar and bass. It sounds like one guitar playing chords, not individual parts playing at the same time. Maybe you could tonally change these and really pan them apart, so the stereo field reveals multiple instruments. It does NOT sound like multiple separate instruments. Does that help maybe?
Gotcha - I kind of get it but I guess what we have is four Les Pauls, or four Strats, not 4 different guitars? They kind of stack up together to make one big sound. A difficult aim, I think, I play bass, and can imagine this one distortion free, but with maybe a rickenbacker edge to it, but clean. I hate distorted bass as a sound - it always to me sounds like somebody who turns their amp up to be louder but gets distortion instead.
I thought I'd see what happened when you pick different sounds and pan these? I wanted to see if different tones became easier to spot. It's a complete pile of poo of course, but I had this really awful file - so I dumped everything bar the notes and tried different sounds - and a twangy, undistorted bass to see if it held together or not. Still not convinced it goes with guitars but a bit of eq, reverb and panning on each track.
Not to pile it on, but I thought a similar thing re: the effect that the distortion / compression has on the dynamic range.
Vivaldi is Vivaldi because it's got those dynamics that were lost, and the parts play off each other, handing the melodic interest around.
Although I can hear that they're played instruments, the compression makes them sound synthesised.
Give it another go letting more dynamics through and only a blues level of distortion?
I'm imagining this done on acoustic guitar which would be more amenable esp. to the classical listener
Alternative ending to this story: Go full hog on the synth aspect and set it up like a game sound track, DnB drums and arrangement!
It's actually within the right tempo range for a fast double time DnB feel round the 170bpm mark
The distorted bass would probably not have even enough distortion in that context.
Running it through a chorus or phaser could give you an interesting Reece Bass