The edit menu lets you add/remove audio machines or open preferences dialog.
Add - select of different machines
Panel - acts as your default sink.
Mixer - enables you to bundle your different output engines.
Drum - is used to do pattern editing using PCM audio files.
Matrix - is used to pattern editing, intended to be linked against Synth.
Synth - is a software synthesizer.
FFPlayer - may be used to open Soundfont2 audio file container format.
Remove - the focused machine.
Preferences - open preferences dialog.
Within preferences dialog you may choose between different topics. For each one one tab.
Sound card is your physical devices to do playback.
Audio channels specifies the audio channels to allocate for output device.
Samplerate affects the entire project. Your audio files have to be at very same rate further your device has to support the given rate.
Buffer size is used for all audio buffers. Your soundcard has to support the passed buffer size.
Auto-sense on stream is required for certain LADSPA plugins but may cause additional performance losses.