You have to have at least one device before you can have a default
[wine] / dlls / dmusic32 / dmusic32.spec
1 1 stdcall CreateCDirectMusicEmulatePort (ptr ptr ptr) DMUSIC32_CreateCDirectMusicEmulatePort
2 2 stdcall EnumLegacyDevices (ptr ptr) DMUSIC32_EnumLegacyDevices