If a theremin design does not furnish a sound sample of the results the designer was able to achieve it should be "red flagged" as probably not having a musical sound much less playable.
A sound sample means a sweep through the range, not a pro performance.
The newbie builder needs to know that just because it says tube/valve does not mean anything special unless the sound furnished is pleasing to the builder. Tubes designs can whistle just like their cousin transistors and not have a throaty sound.
Some transistor theremin designs can sound better than tube/valves.
Theremins are like a box of chocolates "You know the rest of the story".
nieradka's rating system is a great idea.
When it comes to a newbie wanting a theremin I always cringe a bit as I know of something less than desirable with everything available. My thoughts are choose your poison wisely, for I imagine first theremin experiences are mostly short lived.
Edit: Just like the Photo Album there should be a place to upload a single sound byte, having no simple method to do this may be why so many avoid uploading. I just want the newbie to hear the difference between a square wave, sine wave and everything in between.
Christopher