Replacing Microsoft GS Wavetable Synth

In developing the Accompaniment Machine (AMac), I used the Microsoft GS Wavetable Synth as an alternate MIDI output to test port redirection in the program. Until now, I thought the problems of the driver were limited to bad sound and no options (you can’t adjust any sound parameters like reverb, chorus,…). Working with the AMac Performer window, I found that these issues were only the tip of the iceberg. I collided with the GS Wavetable Synth latency flaw. Sounds occur about half a second after the MIDI signal (key press). After wasting some time checking my program, an Internet search revealed that this was a problem of long standing. Needless to say, it is impossible to use the output driver with any type of performance software. In my mind, there are two mysteries:

  • After 15 years of complaints, why wouldn’t a company with multi-billion dollar resources spend an insignificant amount to fix the problem?
  • The official explanation for the delay on the Microsoft site is that the GS Wavetable Synth is a “software synthesizer”. You have to wonder what the rudimentary “synthesizer” is doing for a half second on a 3.5 GHz, Core i7 computer. Perhaps calculating π to 400 million places?

Fortunately, I found a free alternative that resolved all problems. In this article I’ll walk through the installation procedure which includes some non-obvious steps. It involves about 10 minutes of effort.

The primary program is CoolSoft VirtualMIDISynth, which installs as a MIDI output port on your Windows system. The program requires an available sound font (a database of waveforms for MIDI voices). There is a list of links to 10 free sound fonts on the CoolSoft web site:

I picked the high-quality Arachno sound font, available at

Unless you have SfArk compression software installed, download the package in the plain SF2 decompressed format (, 136 MB). After unzipping, the important file is:

Arachno SoundFont - Version 1.0.sf2

Move it to a permanent location on your hard disk.

Return to the CoolSoft site, click on Download in the navigation bar at the top, and download the file


Run the installer and accept the option to run the Configurator after completion. Click the + (plus) button in the SoundFont tab of the Configurator. In the dialog, navigate to the location where you stored Arachno SoundFont – Version 1.0.sf2 and choose it.

Advanced options tab in the VirtualMIDISynth Configurator.

Figure 1. Advanced options tab in the VirtualMIDISynth Configurator.

Run your MIDI software to test the ports. You should see the option CoolSoft VirtualMIDISynth in addition to Microsoft GS Wavetable Synth. Choose it and play some notes. The sound is infinitely better, but you may be disappointed to find that the latency is almost as bad as the Microsoft driver. To fix this, run the Configurator and choose the Advanced options tab (Fig. 1). Lower the value of Additional output buffer from 250 to 5-10. This reduces the latency to a value consistent with performances. Lower values may prevent sending multiple notes (e.g. chords).


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