There are many softwares that are often used. I recommend a very popular software called GoldWave.
Compression method:
1: Search Baidu for the software: GoldWave and download it.
2. After installation, open and display the following interface:
3: Drag the song file to be compressed to the gray area.
4. Click: File-Save As (as shown below).
5: In the pop-up interface, first select the directory to be stored (as shown below).
6. Secondly, fill in the file name, and then select the type of saving: click and select "MPEG Audio (*MP3)" (as shown below).
7. Finally, select the sound quality to be compressed. It is emphasized here that if you choose top-down, the sound quality will be worse, but the file will be smaller. According to your own requirements for file size and sound quality, finally determine the sound quality options to be used (as shown below).
Finally, click "Save".
Suggestion: compress it several times and save it several times. Then, find out the files, test the audition one by one, and choose the most ideal file.