If you could bring back a dead band/musician which one/who would it be?

Mozart. Dude would be social media famous in .2 seconds. He’d be annoying us all. He’d be covering all new songs same day after hearing it once. And I’m here for that chaos.
- It would be a crime if he didn't do a remake of Amadeus, replicated to the letter but for the main actor.
  
  Amadeus Amadeus,
  A-madeus,
  Amadeus, Amadeus
  A-madeus,
  Amadeus, Amadeus,
  Oh, oh, oh Amadeus
  (cue frenetic speech sequence)
- He’d be covering all new songs same day after hearing it once
  So basically Weird Al but faster?
  
  Jacob Collier

Freddy Mercury.
Or David Bowie
- Freddy's voice was fucking amazing
  
  He was also just dahling, seriously

Freddy Mercury
- The starlord provides the only correct answer

Fkn Jimmy Hendrix

Chris Cornell
- It's a tie between Chris and Chester.. both too soon.
  
  I'd say at least bring back someone who wants to be here
- Agreed
  
  Here is an alternative Piped link(s):
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Jeff Buckley, no question. He released arguably the best album of the 90s (Grace) then went and fucking drowned. Only 30 years old. He coulda been one of the best to ever do it, but we're left wondering.
- Here I am, upvoting comments of people who wrote answers first: Bach, Mozart and Buckley. I tend to believe second or third albums are the best ones from an artist, can you imagine if this was true for Buckley?
  Love to basically every mentioned artists, but I think most of them did give the best they had while alive.

Gotta go with chester, assuming you can bring them back with their health (mental and physical) "fixed" to a good massive balance.
Not because he's any better than any of the other greats that have died. Not even the ones that killed themselves.
Just because there's something about his death that makes his life feel more unfinished.
Out of any of the people listed here, I think he had the most undone. Not even in the musical sense alone, across the board.

Chester without a doubt.

Nirvana(Curt Cobain), Linkin Park(Chester Bennington)
- I would suspect Kurt being back could have an impact on the history of Foo Fighters and its success, so I'm.. conflicted about that one.
  
  After a few years, Nirvana split, Kurt goes solo, Foo Fighters are created
- Karen Carpenter - mainly because she was such a talented musician and her death so tragic.

Imo, unfortunately, bringing back Legends will just harm their legacy (I'm thinking of John Lennon, Jimi Hendrix, David Bowie...).
However Tupac may have had an enormous impact in the 90s and early 90s music, and so on.
And who knows how grunge could have gained other mainstream success with Cobain...
- Cobain is risky, odds are he just peaces out again 😞
  
  Depends if Courtney loves aim is still good at this point.

My vote goes for J.S. Bach. One of my shower thoughts is that he would make a great experimental IDM artist. He would give Authechre a run for their money.
- Authechre
  Hadn't heard of these guys. I like them - thanks!
  Reminds me of Noisia and Aphex Twin.
  
  Seconded here, many thanks.

Otis Redding. I didn't realize until recently that he died so young, I would've loved to see how the rest of his career turned out. His voice had such a special quality.
- Mid-century airplanes killed a bunch of famous young musicians.
  Even now: the smaller the aircraft, the less you should want to be on it.

Peter Steele. Although he might disagree. Type O Negative's last album before his death was named "Dead again", and a lot of their music is about escaping yourself (aka suicide or extreme self harm)
- Mine too!

The first ancient cavedweller to stretch skin over a frame and start hitting it to make noises. Give Grog a full drumset and see what he comes up with

Dimebag Darrell.
- I came here to say this!
  I tip my hat to you!

We could really use a Pete Seeger or a Woody Guthrie in times like these.
- Recently wanted to add "this land" to a Playlist, but wanted a more modern cover and it is damn hard to find a version that includes the original lyrics about private property and trespassing. https://www.woodyguthrie.org/Lyrics/This_Land.htm

Harry Chapin
Or
Karen Carpenter
(I know, they're kinda sappy but they were on my Playlist when I was young and in love.)
- Karen carpenter was going to be my answer for this too...

Mark Sandman
- Such a unique talent. Knowing he died of a heart attack on stage adds a whole other dimension to "Do not go quietly unto your grave"

Wayne Static.
- +1

Buddy Holly, Ritchie Valens, and "The Big Bopper" J. P. Richardson
Would have liked to see what would have happened if they had continued making music.
- Hey guys, bad weather up their, I have some nice seats in my bus, I drive, you can rest, ok?

Doom.
I'd be hesitant to bring back anyone who's reason for death was suicide or substance abuse, it just seems cruel.
- Remember all caps when you spell the name.
  
  Tbh yeah, or at least the MF before DOOM is necessary. I was sitting here thinking about Doom the hardcore band until I read your comment lol.

Petri Walli.
Really, it's a friggin' miracle that Jeff Mangum only quit and fucked off for a decade. What all musicians need to know is that success won't fix depression.
- This answer right here.

Ian Curtis (Joy Division), though that would probably screw up the timeline for New Order and all of 80's music (not a dealbreaker).
Prince (obvs)

Aaliyah. 22 is far too young to have died, and her career was moving in the craziest direction. She was set to collaborate with Trent Reznor; I wanna see how she would've changed the game.

Randy Rhoads
- I feel like it's a point against him that his death was entirely avoidable and completely stupid.
  Otherwise? Yeah.

Stevie Ray Vaughan

Jim Croce. He died relatively early in his career and was already an amazing songwriter. What could he have written with more time?
- He would have put it in a bottle

Jimi hands down

Easy: Duke Ellington

Hendrix, Rory Gallagher and SRV. Imagine what the blues and the world would be like with those 3 big hitters still around.

Seriously, so many great suggestions from other people.
I'm going to throw out Neil Peart, although I'm not sure he'd appreciate it. Selfishly, I'd love to have him back.

Liszt.

Bradley Nowell. Sublime was so good, and none of the bands that have followed in their style have had the same lyricism that Nowell had, or have been able to really blend genres like they did to make something completely unique.

I would only suggest Ian Curtis if anti-epilepsy medication has advanced significantly since 1980. Dude had it rough.

- He died before the world learned what a cunt he was
  
  https://youtu.be/duTaVhslT-0
  
  Man Always Gets Little Rush Out Of Telling People John Lennon Beat Wife

Orpheus. I bet he’d do great fronting a metal band.

Johann Pachelbel. So many modern songs reuse the melody from his Canon in D. I just think, it'd be fun to let him listen to them. Would probably blow his mind to listen to modern music, to begin with, and then to have it be his melody, too. 🙃

SOPHIE. Hyperpop hasn’t been the same since her passing.

Biggie Smalls

toots and the maytals

Peter Steele

Elliot Smith, no contest. Best singer songwriter ever.

Chuck Schuldiner. Greatest death metal vocalist to ever live.

Eyedea

FZ
Can't believe nobody else has mentioned him yet

Stan Rogers. Would pretty much double the number of available sea shanties

Justin Townes Earle.

Bryn Jones aka Muslimgauze

Nightbirde

Piotr Grudziński of Riverside. It's clear to me their discography went completely different way than it could have after he died being only 41.

Colter Wall, not that he's dead yet but im gonna save it if he dies before me.

Bob Marley.

Max Bennett. He's not famous famous but he's well known enough in the jazz scene. He played with Frank Sinatra, Dizzie Gillespie, and recorded on countless studio sessions. I knew him personally and I think was his last student before he passed. Some people closer to him than me told me one of the last things he said was "I need to give jcabral9 his lesson" and it makes me tear up whenever I think about it. I was too young to understand most of his concepts--I wish I could know him as an adult and professional musician myself.

Chuck Schuldiner, frontman of death metal pioneers Death, dude died of cancer in 2001 at the age of 34. I never had the chance to see them play live but their records are incredible.
Cliff Burton, Bass player of Metallica, died when the band's tour bus crashed and he was crushed underneath it. The band lost part of its soul and it took them a very long time to get over Cliffs death. Seeing videos of him playing live makes one understand what was lost, as he was an incredible musician.
On a more general note every artist that died very young, many made a big impact to their genre or even to a wider audience without it ever knowing.