Kevin Gates -- Key Witness in Concert Shooting ... Cops Believe

Police in Kentucky want a sit down with rapper Kevin Gates after a shooting at his concert -- a crime they think he can help them solve.

Cops were called to Gates' show in Lexington early Sunday morning after shots were fired. One person suffered a non-life threatening wound ... and a few others were hurt when part of the audience stampeded for the exit.

Law enforcement sources tell us cops think Gates' position at the time of the shooting -- up on the stage -- gave him a unique vantage point, and they're hoping he saw something or someone.

If he did, Gates didn't let on that night -- we're told he actually performed 3 more songs after the shooting ... all while standing in the remaining crowd. That seems like an odd move for Gates (who you might remember from that "I had sex with my cousin" thing) ... if he'd just witnessed a shooting.

We're told cops are getting radio silence from Gates. We've reached out too, and got the same.