The track parameter that is being set or retrieved by one of the SetParam or GetParam methods is identified by a GUID in the rguidType parameter of the method. Each parameter that requires data is associated with a particular data type, and pParam must point to a variable or structure of this type. In some cases, part of the data structure must be initialized even when calling GetParam.
The predefined parameters are listed in the following table, which will take you to tables with more detailed information about each parameter. In the detailed tables, note that pParam and mtTime refer to the parameters of the various GetParam and SetParam methods. Note also that although parameters are always associated with particular track types, most often you will call the method on the segment or the performance and let DirectMusic find the appropriate track. (See Identifying the Track.)