1. A method of searching audio files in a portable audio player in combination with an automobile audio system, comprising the following steps of: reading tag-data associated with each audio file and producing voice data for information retrieved from the tag-data; creating a play list that lists the voice data produced based on the tag-data in an predetermined order where each of the voice data and audio files is accompanied by address data; storing the play list and the audio files in the portable audio player; connecting the portable audio player with the automobile audio system for sending the voice data in the play list and the audio files to the automobile audio system and receiving command signals from the automobile audio system; generating speech sounds based on the voice data in the play list by the automobile audio system in a predetermined order and accepting user's commands through the automobile audio system; and searching an audio file in the portable audio player based on the user's commands.