pureFM software synthesizer

• 8 operators
• 16 note polyphonic
• 16 bit sine wave resolution (16384 samples per quandrant)
• 4096 pitch units per octave
• 16 octave range

Build any algorithm

• All 8 operators may be dragged into almost any arrangement
• Arbitrary feedback path

Envelopes

• Arbitrary number of stages
• Looping
• Selectable key-up point
• Each stage may be linear, exponential, or immediate value with delay

LFO

• LFO has same envelope flexibility as the operators
• Sine, triangle, square, saw up, saw down, noise

Mono mode

• Mono mode with portamento
• Each MIDI channel has its own voice
• Each voice keeps track of highest key down and stays triggered

Source code README:

The "purefm-host" application is the container for the "pureme" app extension. After running the host application, the extension should be available to use as a plug-in in Garage Band, Logic, etc, under the vendor name "Shoes In One Hour" and plug-in name "pureFM".

The host application is a minimal test harness which loads the plugin, allows presets to be saved or loaded, and sends down MIDI data from any inputs present on the system.

The sections of the plug-in are:

• Audio Unit

This is the AUAudioUnit implementation. It glues the kernel to the model classes which provide the patch data.

• Model

These classes own the patch data used by the kernel and provide a KVO bridge to the UI. The root object is an instance of State, which is serialized for the preset data. The audio unit may replace this instance when de-serializing another copy as part of setFullState:, which is effectively loading a preset.

There is also a mechanism to allow running state data to be published back to the model. The model classes present this data back to the application via read only attributes.

This section has its own README file explaining memory ownership model which allows the kernel to see changes atomically and safefly use a weak reference without ever needing to reach in to the runtime library to delete instances or be left holding a last reference.

• DSP

This is the implementation of the synth engine, written in portable c++17. The engine could be cleanly ported to other platforms or plug-in mechanisms from this level. The Audio Unit section instantiates this along with its instance globals and state data, and plumbs the patch infromation from the model.

• UI

The AudioUnitViewController presenting the UI. It can see the patch information in the model classes via standard bindings through the state attribute.