One of my most useful creations is a from-scratch audio engine titled MonoStereo, originally built for the MonoGame framework, but later transitioned to be a universal resource. MonoGame is a modern-day recreation of the discontinued XNA framework, so naturally following in XNA's footsteps, its provided audio features leave much to be desired.

With my own engine however, I can do quite literally anything - from having direct control over sample reading to real-time playback modification, nothing is impossible. MonoStereo is built on top of NAudio, an open-source, C# based audio framework, (and using PortAudio for centralized driver access,) meaning that if something isn't working as expected, it is entirely within the realm of capabilities to simply go and change the behavior myself.

Below is a demo of some of MonoStereo's capabilities.
On the left is a simple program to demonstrate the basic filters, and on the right is a custom filter that I wrote to reverse audio in real-time for a popular Terraria modding project.
Some features, not showcased here, but also supported, include:

• Custom song and sound sources
• Dynamic track layering (more than just 2 layers - multiple layers playing at a time)
• Custom content compiler for all audio tracks with the Content Pipeline Tool
• Sound effect caching for performance and latency optimization