That has a beautiful sound.
I first heard of a mandocello back in 1980 when I bought Cheap Trick's "Dream Police" album. It's listed in the credits as one of the instruments Rick Nielsen plays. But though I've heard the album hundreds of times {it's a great album} I've never been able to identify the sound of a mandocello. And having heard you play this one, the sound that I've thought it is over these years, it clearly isn't.
I do like this sound though.