If you're looking to create custom audio mixers for Windows applications, you'll likely need to utilize C++ or a similar low-level language. Achieving this functionality with TypeScript or high-level languages and libraries is typically not possible.
For implementing per-application audio mixing, one option is to utilize the Windows Core Audio API (WASAPI). WASAPI allows direct interaction with the Windows audio system, granting control over audio settings for each individual application. Developing a C++ application would be necessary to access audio sessions and manage volume levels and other properties.
Another approach is to explore existing third-party C++ libraries such as AudioRouter, which offer higher-level interfaces for managing audio settings for specific applications. These libraries can streamline the process of implementing audio mixing without starting from scratch.
It's important to note that working with the Windows audio system can be intricate and requires a thorough understanding of Windows audio programming. Therefore, it's advisable to delve into Windows audio programming and consider using C++ or another suitable language before moving forward with your project.