All evidence points to one person under the mask.
He also won the CMA for New Artist of the Year in 2012.
There are several reasons why Hayes fits the Astronaut.

Credit: Michael Becker/FOX
First, and most importantly, the voices match up perfectly.
Compare thisperformance onThe Masked Singerto this video of himperforming “Wanted” live.
Let’s break down the clues we’ve been given so far.

Jeff Kravitz/FilmMagic
When Astronaut first walked on stage in episode 7, the panelists remarked that he was not that tall.
Hayes is 5'6", so this checks out.
In that same clue package, there is a loose skeleton’s foot floating around.
The second set of clues, though, really cemented Astronaut’s identity for us.
Hayesperformedwith Wonder at the ACM Awards and onDancing With the Starsin 2013.
Sometimes, it just takes a little help from someone from an organized crime family."
Turns out, Hayesholds the world recordfor playing the most live concerts in 24 hours in different cities.
We rest our case.