When Songtrix plays a song or makes any other sounds within the workspace, it is using a Midi Device to generate the sound.

A Midi Device accepts Midi note events and controller events and uses these as instructions to synthesize the audio stream that you hear.

Midi Devices can take several forms.  These can be:

External - a keyboard synthesizer or sound module can be connected to a port on your computer and act as a synthesizer

Internal - a sound card may be installed in your computer, or this functionality may be already inbuilt to the motherboard.

Software - a software module running on your computer may act as a synthesizer, accepting midi messages and generating sound waves.

You can select which device you want to use with the Midi Setup page.  Depending on the computer, the list of available devices may vary, and each may have a different sound quality when playing the same music.

However, the following devices will always be present, since they have been supplied as part of the standard Windows installation since Windows 98.

Microsoft Synthesizer

This is a very capable synthesizer provided as part of the DirectMusic component of Windows.

It has an adjustable latency which allows fast and reliable response for recording and interactive playing (usually down to 20ms - below this the sound output can suffer from jitter).

It is based the Roland GS voice set, which offers the default General Midi voices, plus about 80 additional voices located on different voice banks.

It does not support channel-based Reverb and Chorus effects, but it does provide global reverb (a single setting for the whole playback performance) which can be adjusted for the song with the Controls page.

Microsoft MIDI Mapper

This is a pretend device supplied by Windows.  It simply passes Midi messages through to the real device which Windows has selected as the default.

It does not necessarily select the best device.  In Windows XP and earlier, you can change the selection in the Control Panel through Sounds and Audio Devices.  In Vista, it seems to be hard-wired to the Microsoft GS Wavetable Synth.

Microsoft GS Wavetable Synth

This is really just a device alias for accessing the Microsoft Synthesizer described above.

However, it is not accessed through DirectMusic, so it has a high latency and does not support global reverb.  As a result it is redundant and should be avoided unless you are experiencing problems with accessing the Microsoft Synthesizer.