Audio output circuit design, audio decoder selection, storage media selection and other issues.

1. Audio output circuit design: Design a suitable audio output circuit, including amplification circuit, filter circuit, etc., to ensure the quality and volume of the audio signal.

2. Selection of audio decoder: Choose a suitable audio decoder, such as an MP3 decoder, to ensure that it can correctly decode music files and output high-quality audio signals.

3. Selection of storage media: A music player needs a reliable storage medium to store music files. You can choose to use flash memory, SD card or other suitable storage media.