I cannot imagine any other methods to create music for the Enterprise.

Oh, silly me. I forgot the most obvious way to do it: write it in IS-BASIC. As you do it in your games, if I'm not mistaken.

As far as I could understand, VGM in itself is an organized collection of register writes. Therefore, writing a player that you use to save those register writes again seems to be somewhat like wasted efforts to me. And then again, you have an unwieldy mass of register writes data like in the case with the SID files. Unless DAVECONV have some aces up its sleeves like pattern recognition and referencing to optimize memory use.

Yes, it is an organized collection of register writes, delay time is set, register, and value, as i remember, but for Daveconv we need all register values written in each 50Hz, so we get a mass of 16 bytes from each frame, and Daveconv will generate an envelope table, and a music data table from the huge register output file.
The problem with Music Box is, it does not handle special Dave effects (It is not a problem for me, because i will never write any music )

I cannot imagine any other methods to create music for the Enterprise.

Music Box 1.2 © 1991, Gyányi Sándor (download)
Rockdigi © 1992, DevilSoft (download)
And there are two more in the ep128.hu utility collection. Obviously, they are outside your comfort zone but nonetheless exist. So you don't have to imagine any.

One solutition could be done, create a VGM player, which saves Dave register values the same way as MIDICONV does, and then we could use DAVECONV to create music binary, and use the player of Daveconv.

VGM players exists for retro computers: MSX, Atari 800, Memotech MTX.
The question here is how compact and convenient this format is for use in demos or games.

As I see some people have used the effects of the DAVE chip just for curiosity (and a funny name).
https://youtu.be/Wll5d2tDrWo
https://www.youtube.com/watch?v=-nc2fOB8a3I

VGM format uses quite big space, and i do not remember how much CPU was used by my player, probably not so much, i remember had problems with sample playback, because the memory paging is way too slow for z80 on Genesis.