From what I can recall about the last time a dev commented on the music system. You, as a player, will pick up an instrument and play a set song, almost rock band style. But, you can only play songs that you have learned from music sheets or directly from another musician. There are supposed to be music sheets that NPCs create, but if you have the skill in both scribe and music, you are supposed to be able to compose your own music within the game.

Again, if I recall correctly, when you compose music, your keyboard basically turns into an instrument, with different keys being bound to different notes. And you play the music and write it down, just like you would in real life. So, while you won't be able to go to a website, download a file and then put it into your game folder to play in-game. You will be able to compose your songs into the game.

This is good information but a much more complicated system than MML. I like it and I don't at the same time. Simply because from a coding standpoint MML is easier to implement and more people who like to compose music in games will be familiar with how to do so.

However, on the other side of that coin, I like the innovation and chance to learn a new music system. It will limit being musical to folks who can actually compose/read music in RL.

Thinking back to the music system in Lord of the Rings Online:

Upon release, there was a simple system where you could play tunes by equipping a pipe, lute or drums and use your computer keyboard like a monophonic piano keyboard - it was a bit awkward and you had only one and a half octaves to play with but some folk could put on really good shows - players would stop to gather round and listen, and even join in with drums. Of course there were always syncing issues and the music was a little thin and not many people were good enough players to make pleasant melodies.

So, they overhauled the system, made an external silent beat to sync to and introduced music notation macros in the form of ABC (which sounds similar to MML.) The idea was to allow those of lesser skill to equip their instrument and 'play' simple phrases with one repeated key press - perhaps changing key at intervals with another key. The more talented players could add an extemporaneous tune over the top of this accompaniment and everyone could join the music making. What actually happened was that people would make tunes and even fully fledged multipart musical scores in ABC that played with one keypress for each instrument/player. They sounded great, but it wasn't really live music being played anymore - just a computer program running and a lot of the excitement went out of the system.

Having a system which requires real, continuous input from the player makes the musical play more real and enjoyable. For many people, it appears that the Rock Band style of play is more than enough to engage them - it is, presumably, the closest they will ever get to creating music and I guess it might allow some small degree of emotional shaping of the music by anticipating or delaying the beat - or even forcing the tempo, if it is cleverly programmed (oddly, things that you must strive to avoid doing in the Rock Band style of gameplay.)

For me, trying to peck out The Blue Danube Waltz on a QWERTY keyboard while my friend tries gamely to keep his simple three beat drum/snare accompaniment on the beat (with 100ms pings to the server for each of us) was a joy and frustration that I'd love to revisit.