An operating system program launch menu, such as a Start menu, provides various mechanisms for a user to quickly and efficiently locate and launch desired data items such as programs, data files, storage locations, and the like. The chord tubes are interlocked by means of the provision of a plurality of equisized, equispaced, longitudinal ribs formed along the length of the depending side arms of the U-shaped chord tubes defining elongated recesses therebetween, the ribs on one of the chord tubes being adapted to interlock into and mate with the recesses defined between ribs on the adjacent chord tube and vice versa. Nulls between sensitivity lobes are widened, effectively narrowing the sensitivity lobes and improving directionality and noise discrimination. The securing ring of a proper thickness sandwiched between the soft and coarse sponge is provided with a tubular central hole with internal threads defined therein so as to permit the connector to be removably engaged with the securing ring. The collar has an outer surface serving as a bottom surface of a V-groove defined by the respective conical pressure surfaces of the fixed and the movable sheave of the drive pulley, and a conical surface forming a central part, around the drive shaft, of the conical pressure surface of the fixed sheave of the drive pulley.