'Duck Dynasty' Star Si Robertson -- Rocking Out in Nashville With Local Band

"Duck Dynasty" star Si Robertson got real country Friday in Tennessee ... no, he didn't hook up with a family member -- the reality star rocked his ass off.

Robertson linked up with The Mauldin Brothers at Rippy's in Nashville to perform a few songs ... and for some reason Si brought a blinged out microphone along for the ride.

The 66-year old attempted to hit some difficult notes while he sang to a surprisingly packed audience.