I’ve posted about many free web applications that allow students to compose a song and then post its url on a blog or online journal. You can search through the posts tagged as “music and art” to find them.
Here’s another one. It’s called Jam Studio and seems pretty easy to use. English Language Learners could very quickly compose a song, email and post the url, and write about what they can visualize as they listen to it.
I’ve posted it on my Examples of Student Work page under Student Songs.