I want the sound to sound at any speed.

[YOMA8338]

If the tempo is above 20, it will occur that some notes will not sound.
If such sounds were made to sound on the front or back ticks, all sounds would sound in music with a tempo over 20. (Whether the music would be strange or not.)

[YOMA8338]

I set the tick rate to 40 with the tick command and played music with a tempo of 31.86 t/s. Since it played correctly, is it possible to set the tick higher only for the sound of this plugin? (I feel like it is indeed impossible)

[koca2000]

This is a know issue caused by the synchronization with the server's thread using the BukkitScheduler. It is also one of the main reasons why I am working on a complete rewrite of NoteBlockAPI in version 2.0.

[YOMA8338]

Will version 2.0 be updated for use with 1.21, or will elements of 2.0 be ported to the regular one?

[koca2000]

Version 2.0 will be compatible with Minecraft versions 1.8 and newer and will be backward compatible with plugins for 1.6.x as much as possible.

[YOMA8338]

Where can I get the NoteBlockAPI for version 2.0?

[koca2000]

It is not released yet. The backward compatibility layer is not finished and there may still be some bigger changes so the code is not public for now.