AyyiGtk is currently the main Ayyi client application.
It provides a fairly conventional audio sequencer user interface with an emphasis on flexibility and uncluttered display.
It is built around the concept of Panels. Any number of panels can be arranged as desired. Panels can be statically linked (in-application), dynamically loaded (in-process plugins), or even separate processes (external plugins).
The main panel is the Arrange panel. This is where tasks can be accomplished, with supporting panel types available for specialized tasks such as mixing. The original Arrange canvas is/was implemented using Gnome Canvas but the more recent implementation uses OpenGl and is more performant and visually nicer. MIDI is not yet supported in the OpenGl canvas.
AyyiGtk uses the "Ayyi Model" client c library which provides relatively high level access to the Ayyi model.