Zed Synth from Richard Meyer is available for for iPhone & iPad. Here's the description of it from the App Store:

Zed Synth is easy to learn, with live graphs throughout and built-in help for every knob, but it's a real powerhouse synth combining virtual analog synthesis with physical modelling. This innovative blend of technologies allows you to create rich and immersive sounds, ranging from bright electronic dance music patches to subtle and expressive solo instruments.

Zed Synth is also a unique audio effect processor: you can route external sounds through the synth and completely transform them: use the microphone and transform your voice, turn drum machines into strummed guitars, or radically transform the sound of any other Audiobus-compatible app!

Over 140 presets covering a wide range of styles provide a great starting point to making your own music. And you can easily share your patches with friends and other IOS musicians.

Key features:

- Wave-Shaping oscillators: inspired by 1950s vacuum-tube technology, 4 parameters allow you to create a vast array of original oscillator shapes which can be modulated in real-time.

- Physical Modelling: a sophisticated resonator can be either struck by a mallet or excited by the synth section (including external audio) with different forms of interaction to simulate blown, bowed or struck models.

- Unique Audio effect: the Zed Synth can process external audio via Audiobus and pass it through its string model. This unique effect can turn unpitched sounds, such as beats, into pitched sounds, akin to what you could do with a vocoder, only more responsively and with a much richer timbre. Using this approach, Zed Synth can radically transform the sound of any other Audiobus-compatible synth on IOS.

- A unique "Spring Box" effect capable of emulating the full 88-string sympathetic resonance of a piano soundboard, or simulating the body resonance of a musical instrument.

- Oscilloscopes throughout the user interface provide clear visual feedback and ease of use.

- Built-in Help system throughout the app to explain each of the modules and all the parameters.

- A Powerful Modulation system makes it incredibly easy to add modulations from a variety of sources to any of the synth's parameters.

- The Granulator: a different take on the ubiquitous arpeggiator, the granulator can periodically or randomly retrigger the sound, and also vary the pitch. This makes it possible to create rhythmic chorded sounds with a human feel to them, or completely chaotic sounds like raindrops on a tin roof.

- Synth Overview displays the signal path and routing of the various modules, as well as making it easy to jump around sections when editing.

- Effects to further enhance the sound, including a stereo expander to enrich the spatial complexity of the signal.

- iPhone support: Zed Synth has been specially developed to run on both iPhones and iPads. Actual polyphony will depend on the speed of the device and older devices will not be able to recreate a full 88-string piano reverberation effect.

- Patch Sharing: Zed synth makes it easy to import & share patches with friends via e-mail.

- MIDI Learn mode so you can quickly & easily map your MIDI controller's knobs to the synth's parameters.

- Audiobus (including presets), Inter-App Audio and Core MIDI.

- 4x Oversampling: this greatly increases the quality of the sound and reduces aliasing at high frequencies. It can be disabled to reduce CPU utilisation.

Pricing and Availability:
$9.99

More information:

• App Store