说明：  Dmusic 口驱动开发，开发工具：winddk
(This sample is a DMusic UART miniport driver, which provides an interface to the MPU-401 chip. The DMusic (DMUS) port driver, which is built into PortCls.sys, insulates this miniport and connects it to the rest of the system. The sample handles one input stream visible to either DirectMusic or midiIn APIs, one output stream visible to midiOut APIs, and multiple output streams visible to DirectMusic APIs. It compiles in the 64-bit environment and is compatible with both Alpha and x86 platforms )