: This service allows you to upload and copy a share link quickly. 3. Messaging Apps

If "posting" means sending it to a specific person or group:

Most social platforms don't allow direct MP3 uploads. Instead, you should upload the file to a host and share the link:

: You can attach the MP3 directly as a "Document" or "Audio" file for instant playback.

If you want someone to download the file directly, use a cloud service: