Through property sets, DirectSound is able to support extended services offered by manufacturers of sound cards and their associated drivers.
Hardware vendors define new capabilities as properties and publish the specification for these properties. You, the application developer, can then use the methods of the IKsPropertySet interface to determine whether a particular set of properties is available on the target hardware and to manipulate those properties, for instance by turning special effects on and off.
Property sets allow for the unlimited extension of the capabilities of DirectSound. You use a single method, IKsPropertySet::Set, to alter the state of the device in any way specified by the manufacturer.