IMHO, not the best solution: there will be a need to syncronize content of descript.ion and corresponding folder.
For example, let you have a folder with 20 *.mp3 files, after when descript.ion has been created, user add 10 files more.
mp3toin should be called to update descript.ion -- and how to determine when?
My opinion: HFS does great job already it can use descript.ion, and, in my experience, descript.ion for mp3 files doesn't change very often. So let spend 30 minutes to update all folders, and then update only when it needed.
But it my imho