The light beam deflection cycle of a rotational polygonal mirror includes first and third sections in which a latent image is not formed, and a second section in which the latent image is formed. Selected parts of the stored data are mapped to corresponding parts of the helical path to facilitate visualization of the stored data. The system also includes transmitting structure for transmitting sound signals from a sound signal source to the speakers of the earpieces in a manner transmitting a separate sound signal to each of said speakers in each of the earpieces. The lossy files may be de-featured and transcoded before concatenation. The present compounds lack a 1,4-bridging group as found in the ecteinascidins. The cover body, the emitter, and the receiver cooperatively close the open end of the receiving space.