Wolfgang Palm has released a free version of PPG WaveGenerator! The key difference between the free and $20 versions is you don't get to play with the synthesis bits in the free version, but you can play with all of the presets to hear how this synth sounds.
"The strength of the PPG app is the sound, this can only be experienced when hearing it. Sometimes apps are not suited to the person buying them and we thought having to buy an app to find this out was not good. This allows everyone to try before they buy."-Wolfgang Palm
PPG FREE is a feature-limited version of the PPG WaveGenerator App. All editing functions are disabled, voice count is 5 maximum with a sample rate of 44.1Khz, but the user still has access to a selection of the incredible library from the full version. To benefit from the full power of the PPG synth engine users will need to purchase the PPG WaveGenerator App from the App Store.
My tutorial will probably not be useful for the free version, but I'll include it here to show off what the full version can do.