https://itunes.apple.com/app/id1458743434?mt=8&uo=8&at=11l4Kv
Sugar Bytes is a German company that makes plugins for IOS, among other formats. Their most recent IOS release is a synth called Factory, which is really a gas. You can find numerous reviews of it, as well as video demos. It costs $18, although you can get a limited function version of it for free. The full version includes 400 presets, and it is easy to make your own sounds as well.
Many of us like Sugar Bytes, and they have a number of cool synths among other things. Factory is an example of a synth they released on MAC and Windows a couple of years ago. In those formats the identical synth was $130 or $140 list. Stuff ported to IOS is usually drastically cheaper, even for identical programs.
It costs software makers virtually nothing to distribute software via the App Store, which is the only sanctioned way that people get IOS apps. Additionally, the makers get 70% of the gross reciepts from each app, which is much more than they get from the traditional distribution methods. Keep in mind Apple collects all money, and pays the limited cost of customers downloading the apps.
Not everyone is wild about Apple’s distribution model, but it seems to work pretty well for a lot of small companies. From the customer’s point of view, it’s very easy to download apps, and you can re- download them as many times as you like. You can also put the same apps on all your IOS machines for no additional cost. There are virtually no viruses, and apps in general are dirt-cheap. There is also none of the copy protection that can sometimes be exasperating on other formats.
IOS Music Making 