QuikDaw (provisional name) is a general Digital Audio Workstation written in C#.NET, and heavily based on the NAudio libraries by Mark Heath and VST.NET libraries by Marc Jacobi.

The General Midi sounds that are included in QuikDaw are produced by BassMidi VSTi, a free SoundFont player by Falcosoft, consuming the soundfont: Reality_GMGS_falcomod.sf2 (version 1.2) , also provided free from Falcosoft

It was originally started as a personal project for learning how to mix audio in Windows in .NET but over several years gradually evolved into a kind of multi-featured DAW with many of the common features often found in audio workstations, including (theoretically but not really) unlimited tracks (audio and midi), editing of multiple clips per track, VST/VSTi (ver2, 64-bit only) support, volume/pan automation and Midi editing functions.
QuikDaw is very much a work-in-progress (it even needs a better name someday...), but it's fully free to use (installable on Windows .NET 6 or higher), and I've also made the code available to browse here, though the full code is not in any downloadable form (yet).

Incidentally, the performance QuikDaw provides is certainly NOT on the level of commercial DAWs, but it can be reasonably sufficient depending on the project at hand, assuming modern CPU speeds and memory. So far I've used it to edit a few hour-long podcasts, with up to 10 tracks of voice/music, and reasonable numbers of VST effects, without pushing things too far.

For me it would have been impossible to even consider making without the existence of the robust .NET libraries: NAudio and VST.NET, so the utmost kudos go to their respective authors.