thesoundtestroom did an excellent demonstration of setting up Inter-App Audio in the current batch of available apps. He closes the video out with additional tips on configuring Looptical for use with Audiobus.
Zlata Brouwer from Violin Lounge looked at some free iPhone tuners. There is also AccuTune by Jam Up developer Positive Grid, which is nearly free at $1. The focus is, somewhat obviously, on tuners for violins but these are good suggestions in general.
For what it's worth, my favorite is Tunable by the Nodebeat developers, which is occasionally free.
One Red Dog has released their long anticipated followup to Artic Keys! In the increasingly crowded subtractive synth app market, Arctic ProSynth distinguishes itself with an extremely wide sound. Some may call it a "fat" sound, but I don't think that quite does justice to the Hyper™ oscillators here. You've got your basic unison mode, but Hyper also offers tuneable and mixable unison for each of the two main oscillators independently. Unison ontop of Unison, with control over it all. Fat? Phatt? Nah, this is Behemoth.
Arctic ProSynth iTunes Description:
Arctic Pro Synthesizer / Vocoder is a modern subtractive synthesizer for the Apple iPad. It does not aim to accurately model or re-create vintage synths of yesteryear. Instead Arctic ProSynth offers the contemporary synthesist a rude, rough, bold and tough palette of sound to get stuck into. Including two HyperOscillators, a sub oscillator, dual filters, and easy to re-order master effects. The Vocoder gives you an extra dimension to your musical performance.
Combine two HyperOscillators and one Sub Oscillator for some seriously fat sounds. Layer up to 8 oscillators in unison to create very thick and powerful tones. Spread detune and Mix these separate oscillators in real-time. More than just a "SuperSaw" - it's also a Super-square and Super-triangle.
Legendary sound designer John ‘Skippy’ Lehmkuhl has exclusively designed the factory presets. John has worked as a professional sound designer since 1988 for Korg - making patches, combinations, drum kits as well as creating the sample data for almost every synth Korg has released since the M1. We have drawn upon his vast experience in the development of the audio engine.
Arctic ProSynth includes everything you need to record and share your audio and MIDI with others. Live record to WAV and MIDI files. Upload to SoundCloud. Paste the audio using Sonoma AudioCopy, open in other apps, or share with Kymatica AudioShare. Presets and Banks may be emailed and transferred via Wi- Fi and iTunes Files Sharing. Supports Audiobus input slode to stream live audio directly to other Audiobus- compatible apps.
Key features at a glance:
Process live audio input from a microphone with the Vocoder
Up to 17 oscillators per voice with 4 voices
Dual multi-mode filters with adjustable routing
16x4 gate step-sequencer with deep modulation destinations
Ro-orderable effects processors including EQ, distortion, chorus, phaser, delay, reverb and vocoder
I've been involved in the beta testing on this one and have been having a lot of fun pushing the Hyperwaves, and all of those sequencers! In addition to the 121 presets by Skippy there are also 46 from Sunsine Audio!
Here is a playlist of individual overviews, for the 5 main sections of the app.