Q: How can we play music without resource pack on server?
A: Obviously, this plugin it is.

This plugin can import the .MID or .MIDI file. Then it will read file and convert to plugin format.
You can durg your file to plugins/NoteMusic/mus/ . Use command /notemusic importmusic <File Name> to import the music.
If you import done, you can back to the game and use command /notemusic playmusic <Music Name> to enjoy the music.

Well... There are too many commands need to type. To a simple way, you can use command /notemusic gui and... That is! You are successfully opening a chest menu from this plugin and if you has enough permissions you can do any action you want in this plugin menu.

For adventure action, you can also use command instead of the chest menu. You just need type /notemusic help and you can see all the commands.

Wait...If your version is not 1.12.2, you may need to edit plugins/NoteMusic/instrument.yml to your version object. Below here will send a replacement file for 1.8.8: https://github.com/CoolCLK/NoteMusic/blob/main/src/main/resources/instrument_1.8.8.yml

Have fun