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PHAT is a collection of GTK+ widgets geared toward pro-audio apps.

Audio driver classes provide an abstract audio device layer, which transparently supports ASIO, DirectSound, CoreAudio and ALSA devices.

Midi Midi input/output support on Mac and PC Midi message wrapper classes make it easy to manipulate midi using a high-level programming interface Midi buffer classes for efficient collating and editing of midi streams Midi keyboard state objects will monitor a midi stream and provide information about the state of a virtual keyboard Classes for merging and re-timing midi input streams to synchronise with audio streams. Support for reading/writing standard midi format files.

The first basic idea of the glitch-free playback model (a better, less marketingy name is probably timer-based audio scheduling which is the term I internally use in the PA codebase) is to no longer depend on sound card interrupts to schedule audio but use system timers instead. System timers are far more flexible then the fragment-based sound card timers. They can be reconfigured at any time, and have a granularity that is independant from any buffer metrics of the sound card. The second basic idea is to use playback buffers that are as large as possible, up to a limit of 2s or 5s. The third basic idea is to allow rewriting of the hardware buffer at any time. This allows instant reaction on user-input (i.e. pause/seek requests in your music player, or instant event sounds) although the huge latency imposed by the hardware playback buffer would suggest otherwise.