Hi Sandy, I understand what you're saying but I'd like to clarify a couple of points.

It might not be totally clear from the video but the glass is only to contain the sand. The piezo microphone is not like a condenser or dynamic microphone, there's no *ting!* recorded, only the grains of sand rubbing against the piezo are recorded. I used a glass just because it's transparent, I could have used a paper cup or a wooden box and the sound would have been the same (but visually less interesting because you couldn't see the sand moving).

When I'm playing the groove at the beach it's not my flesh hitting the sand, I taped the piezo to my fingers, again, it's the sand hitting against the piezo transducers. I could have used gloves and the sounds would have been the same.

Ultimately this video is not to make sand sound like a grand piano or a guitar, it's a sound design experiment and it might sound nice or not depending on personal taste.

Have you ever heard of booming sands? Those masses of sand moving and producing a loud tone? Some people that have heard them say that they sound pretty interesting, even if it's just sand moving against sand. It's one of those fascinating mistery of nature! :)
Peace.

Technically, you didn't read the description of this project : )
Every sound you hear in the video is made from sand.
What I'm playing on the keyboard is the tuned noise of the sand, mapped into a sampler. The melody, the chord sounds, the bass, everything is extracted from sand noises.