Those who use music notation software are undoubtedly familiar with the two big ones: Finale and Sibelius. There used to be Web 2.0 tools where one could share scores produced by the respective software. For Finale, it was Finale Showcase, and for Sibelius, it was SibeliusMusic. However, Finale Showcase has shut down, and SibeliusMusic is closed and is succeeded by Score Exchange. (I am a Finale user, so I do not know how SibeliusMusic/Score Exchange works.) I found another Web 2.0 tool, however, for music: Noteflight.
According to their About page:
Noteflight, LLC is located in Boston, Massachusetts, and is dedicated to reinventing the way that people create, share and use written music. Our product doesn't merely improve on other music notation software: it lets written music take advantage of the full power of the web as we know it today. Noteflight is a powerful full-featured application to edit, display and play back music notation in a standard web browser, integrated in an online library of musical scores that anyone can publish, link to, or embed.
As with other tools, you have to create an account first. There is a free membership, but there are some limitations. For instance, you can only create up to 10 scores, you cannot print individual parts, you cannot mix the audio, etc. For more features, you will need a paid membership ($49 a year), which they call "Noteflight Crescendo." Once you create an account and sign in, every time thereafter you access the Noteflight website, you will see your own "home page" with information about the scores you have uploaded.
With Finale Showcase and SibeliusMusic, you needed the corresponding music notation software to create your music scores. With Noteflight, however, it's all built-in. I think, however, that it would be helpful if you have experience using Finale and Sibelius -- there are so many notes and symbols that you can type into the score that it can be overwhelming.
It looks like for me that Flash is used to make the music creation work. You can import/export to/from different formats, though I have not tested this. You can add or remove staves as necessary. You can play back what you type in, but on my computer it didn't sound the greatest. Check the User Guide to see all the things you can do.
I finished notating a piece, an SATB chorale by J. S. Bach. You can look at it more closely and have it play back here.
It did take me over an hour to type all of this in, for only sixteen
measures. I hope that it will take less time the more I use it.
You can create our own music compositions, or you can notate existing music (as long as you respect the copyright) Of course, there are options to share your work, as you can see in the below image. You will need an account, I believe, in order to comment on other people's work.
I must say, Noteflight is an awesome tool. I am also an amateur composer, and since I have no aspirations to become the next Beethoven, I may notate my own music on Noteflight and share with others to get feedback. If you have experience with music notation, I welcome you to try out Noteflight.