You can play it like the many theremin style applications thats out there this though being polyphonic and it contains something that I would like to see implemented more often at least in some more experimental synthesis apps and that is that the developer have built in some fluctuations and instability into the sound which makes it more organic.
I do wish that he expands on this idea but maybe giving more controls over the sound as like said before, as it is now it is just one basic sound.
He have used the programming language Csound that is since some time possible using for Android applications it is also as the name suggests a programming language dedicated for developing applications / programs for sound. If this is interesting for you the developer of Moonsynth have written an article / tutorial how he went about making his two applications. The Source code is also available both for this one and his other application that is somewhat limited but nevertheless interesting specially for you noise hounds out there, that one being called Psycho flute.
He released Moonsynth about two months ago and was going to write earlier about it but felt that I wanted to record something using it and tried to fit it into a piece of music that it did not work for, luckily the Developer played this synthesizer as part of a live recording on a radio program so you can hear how it could be used. The radio show is also interesting for some of you as it does shows in a drone / experimental / noise stylelelee.
So he was in the second half of the program that is possible to listen to directly here but there is also a link to the radio show channel for anyone that would be interested in browsing and listening to the other shows as well.
Both Moon synth and Psycho Flute is for free and without publicity.