Portable apparatus for recording or reproduction of sound, including those of pendant types, wrist strap types, and headset built-in types; headphone-type audio playing/recording apparatus; components for all the aforementioned goods, including: wrist bands, headphones, neck straps, arm bands, extension cords for headphones, and liquid crystal displays; electronic memories in the forms of cards, sticks, tapes or disks for use with the aforementioned audio players; adapters for use with the aforementioned electronic memories; USB read-write cables; computer software for encoding/decoding sound data; and parts and fittings for all the aforementioned goods