To disable download option in audio for HTML5 audio and video player add the following tag to audio. and this tag also works in video file.
controls controlsList="nodownload"For Audio:
Add this tag in your audio code, to disable download option in audio.
<audio controls controlsList="nodownload"><source src="song.mp3" type="audio/mpeg"></audio>
For Video:
<video controls controlsList="nodownload"><source src="video.mp4" type="video/mp4"></video>