The mmioInstallIOProc function installs or removes a custom I/O procedure. This function also locates an installed I/O procedure, using its corresponding four-character code.

More info on mmioInstallIOProcA in Windows Dev Center

Exported by

sizefilenameversion
126056winmm.dll6.3.9600.17415 (winblue_r4.141028-1500)
104960winmm.dll1.0.0.0
88576winmm.dll1.0.0.0

Imported by

sizefilename
126056winmm.dll
229376E310688FB4B9AE14D1FB5257F93F3354