Nice to have an alternative to Lilypond (lilypond.org), but given the extreme complexity of notation, I would bet that any brevity gains are short lived.
For those Asciidoc freaks among you, Lilypond is fairly easy to get running in your Asciidoc toolchain of choice. I use the DocBook PDF pipeline, and the lilypond output is quite nice looking. It's awfully TeX-like.
But does Lilypond generate responsive sheets?
That to me was the coolest part of this (apart from what others have said, the power of modern CSS)
Yes, lilypond generates SVG that rescales smoothly
So the measures on a line automatically wrap if viewed on a phone?
They can be rendered at any size.
A PDF is still not that responsive. Clean HTML/CSS is.
Not everyone needs to typeset a full symphony with all the crazy notation for every single instrument though, having an easy responsive web presentation for even 50% of the "simple" scoring you do is a fantastic option to have.
But this solution won't even get you that far, let's be honest.
Can't say I share that conviction? This is absolutely perfect for stuff like "I came up with something, let me score it and share it" without having to reach for notion/musescore/etc or lilypad.
I would also suggest checking out ABCjs for web rendering.
If you can make do with a more limited feature set, I'd properly go with a CSS alternative, rather than using Lilypond (depending on your environment and use case). Lilypond is fairly complicated and not without security risk and have been used as an attack vector due to it being able to embed Postscript.