The bug

The minecraft:event.raid.horn sound is very silent. In sounds.json, its volume is set to 0.01, which is unusually low.

Original description

In a singleplayer world, created with 1.14.3, issuing the command '/playsound minecraft:event.raid.horn ambient YourCoal' did not play the raid horn. I also went to worlds made in previous 1.14 versions and had the same effect.

Steps to reproduce:

1. Create a singleplayer world (or load an existing one works as well)
2. Issue command '/playsound minecraft:event.raid.horn ambient [username]'
3. ... no sound?

Besides ambient, I also tested with block, hostile, master, music, neutral, player, record, voice, and weather, and still had the same outcome.

I also went to a village and started the raid, the horn played correctly. This is a matter of the command I believe.