There are some powerful new iOS apps coming out of the Audio Damage camp. Many of them are free, the rest are very reasonably priced, and all the ones I've tried are awesome.
I just spent some time exploring Audio Damage's new iPad app, Phosphor 2, which is a vintage digital additive synthesizer modeled after the alphaSyntauri. It's got a great 80's digital sound, similar to FM synthesis, and is really easy to program. The good news about the iPad app is that you won't need an ancient Apple computer to operate it.
In the video, I use StudioMux to run audio and MIDI between the iPad and Ableton Live using just a Lightning cable. StudioMux essentially allows you to use iOS apps like any other 3rd-party plugin for your DAW. It's a must-have app and has made using my iPad with Ableton Live a breeze.
The drums in the video come from Mode Audio's new Drum Redox collection. It's a really cool collection of drum samples that are combined with an array of field recordings to create some cool crunch and texture to each sound... definitely unique.
Because I was having so much fun making a little jam, I decided to use some Audio Damage's FuzzPlus 3 and Rough Rider 2 for iOS. Both of these apps are free and extremely useful. FuzzPlus is a nice distortion unit with a cool sounding low-pass filter. Rough Rider is a compressor with a lot of attitude. It really injected a lot of life into the drums.
Check out the video, which will give you a nice sense of what these apps are capable of, as well as how to easily connect your iOS device to your computer with the Lightning cable.