If you could bring back one great artist that has

departed our world who would it be? We have lost some incredibly talented artists, often under tragic circumstances. If it were possible to have an encore I would vote for Janis Joplin. You?
Ricky Nelson, George Harrison, Elvis, Buddy Holly. 
... ONE OF THE GREATEST MALE VOICES (and a tremendously creative individual): NAT KING COLE
Lemmy Kilmister of MOTORHEAD! "We are NOT Metal, We ARE Rock-n-Roll"!
I would love to hear new music again from Tom Petty and Freddie Mercury two legends who wrote and performed some wonderful music. I have built my system around their music it sounds amazing. 
Emily Remler. If you are into great jazz guitar you know who she is. She was an incredible talent. So sad. Get all of her vinyl on Concord. Great stuff and recorded well. 
List is long especially if you include classical but in my lifetime I am most saddened by the loss of Michael Hedges.
The Big Bopper and Richie Valens
That’s an easy one, Geoff. You could do it by just landing one plane safely. Hell, Buddy Holly could be thrown in for good measure as well.
Prince, or since he passed, the Artist Formerly Known As Prince.