Real-time Dynamic 3D Instrumental Sound Library

I want a way to dynamically play instrumental melodies (using SoundFont instruments, or something similar) in 3d positional sound, where the instruments can have different points of origin in 3d space, and can move in 3d space independently of one another. The melodies will not be preset, and will instead be generated at runtime. Your task is to develop an easy to use library and API, for creating instruments, playing musical notes / frequencies for fixed durations on the instruments, and moving the instruments in 3d space relative to the listener. You may choose either C# or Python to expose the API. You may choose any language for the underlying implementation / integration. Attached is brief spec of requirements, constraints, etc.