1.iTunes: iTunes is Apple's music store, which provides a large number of music resources for users to download. Users can purchase and download music in mp4 format through iTunes.
2. Amazon music: Amazon music is Amazon's music store, and it also provides a large number of music resources for users to download. Users can purchase and download music in mp4 format through Amazon Music.
3. Google Play Music: Google Play Music is Google's music store, which provides rich music resources for users to download. Users can purchase and download music in mp4 format through Google Play Music.
In addition, some other music websites also provide music downloads in mp4 format. Please note that downloading and sharing music should comply with relevant local laws and regulations and should not infringe copyright.