For some reason I decided I wanted a theremin, then found this theremin app on Amazon. If you want I'd suggest you get the free version and I use the play store as Amazon decided I didn't own a number of apps I'd downloaded from them. Suggestions were made that I could deinstall go and do something online and then reinstall and then they might work. My time is worth a lot more than the the few pounds I've lost, so I use Google Play Store, as my Samsung Note 4 is Android (although BlueTooth doesn't work now and Google & Samsung like Apple won't acknowledge that the problem exists, so I have to use wired headphones).
Anyway I'm still playing with my Tascam home studio and the theremin will be great fun to add to the recordings. My phone also has a great drum machine on that I paid for from the Play Store (Rock Drum Machine) so along with my guitars, keyboard and voice I have everything I need to do what I want apart from the ability to play or sing properly, but it's amazing that now you can have a full studio effectively in your bedroom.
Apparently the theremin was invented accidentally (it was meant to be an alarm) but Leon Theremin (Термéн) patented it in 1928 (see here)and it's been a staple of many science fiction soundtracks and even Midsomer Murders!
I've included "Noises For The Leg" by The Bonzo Dog Band so you can hear a theremin in action, and a live take so you can see a leg theremin in use in Brighton. Have a great Tuesday everybody.