From a personal standpoint, I don’t feel that a single instrument would necessarily devalue the subscription. It more likely than not would be more incentive for users to subscribe, showing them the new sounds that they will be getting.
My cousin actually was considering Auxy, but was turned off by the lack of sound. After trying to show them what used to be free, they said that would have been enough to convince them to subscribe. That can’t speak for everyone, of course, and i’m definitely not intending this negatively, but I don’t persoanlly feel the demo of Auxy incentivizes users enough to make the plunge into the subscription.