A music recognition method and system for retrieving metadata based on content associated with a media file. The flexible ring is formed as one piece with the handle of the wrench. A second module determines a motor assist command based on the gain curve. , objective lens system, four intermediate lens systems, and projector lens system. Furthermore, the invention includes two types of common device drivers to be registered in an OS to have different priorities, and provides a common interface that does not allow the application to recognize their difference.