How to make the simplest sound synthesis in iOS?

Question

iOS

I came up with one sound thing for touch devices, I want to quickly make a prototype on iOS. If I can somehow manage the interface, then I need help with sound synthesis. I do not even know where to start. I already have a working prototype on JS in Chrome, but without multi-touch with the mouse it doesn’t work at all ...
From the synthesizer I need a very primitive thing: turn on / off a sinusoid of a certain frequency and amplitude. There can be any number of them. Something like that:

sound1 = Sine(frequency=440, volume=0.5)
sound2 = Sine(frequency=440 * 3 / 2, volume=0.3)
output.add(sound1)
output.add(sound2)
sound2.volume = 0.9
output.remove(sound1)

In the synthesis of sound, if anything, I'm not strong, but I know music theory well :)