Digital songwriting

A group of amateur musicians have developed software to enable even novices to write their own songs. It's called MySong and it was developed by Ian Simon, a graduate student from the University of Washington, while working at Microsoft Research with Dan Morris and Sumit Basu. While they don't expect it to produce a hit song any time in the near future, they see its value in enabling untrained users to share in the enjoyment of the creative process of songwriting without struggling up the steep learning curve of music theory and mastering an instrument. After all, everyone has a voice.

How does a musician usually write a song?

There are no hard and fast rules, but typically they first come up with a tune in their head, and then grab a guitar or piano and try out which chords sound best with the melody. If they are worried about forgetting the new tune, they might first rush to their PC, start up their favourite recording software, and commit the idea to hard disk before it's too late.

In any case, many amateurs find it difficult to discover the "right" chords for their new tune, so this is where MySong steps in. The user has to do little more than sing their melody, and MySong does the rest.

Is it really that easy?

This is how you use MySong: first you choose a tempo, using the tempo slider to set the digital metronome. Then you hit the record button, sing your tune, and hit the stop button. MySong then comes up with a sequence of chords to match your melody. Sounds simple?

But how does it work?

Before it can choose the chords, MySong has to work out what notes you sang. This sounds easy, but sung notes are not pure tones: a lot of singers, at all ends of the ability spectrum, sing with vibrato, which can confuse a computer when it is trying to recognise your notes. And then there are those notes that didn't quite come out right (see page 4 for how to fix them), and the fact that the notes might not align with the notes on a piano, but fall somewhere in between. MySong assumes that you get all the notes wrong by roughly he same amount, so it shifts everything by that amount and then locks it on to the nearest musical note.

MySong has a database of 300 songs from which it learns how to associate chords with any given melody. It does this by extracting two types of information: what chords sound good after each other (this is called the ‘transition matrix') and what kinds of melody notes are usually associated with each chord.

Obviously you don't want the same chord every time you sing a particular note, so the chords are chosen using random numbers and probabilities. Also, you can influence the way chords are chosen using the 'Happy Factor' Slider: this tells the software how much to favour major (happy) or minor (sad) chords. Another control is the "Jazz Factor" slider, which determines how often surprising or unconventional chords appear in the song.

Finally MySong's chords are output to PG Music's Band-in-a-Box software, which creates a complete accompaniment from the chord sequence. In less than 5 minutes of work, you've got a complete song.

Does it sound good?

For a given melody there are many possible chord sequences, and there are no "right" or "wrong" answers. The only way to assess the system is to ask people to listen to the melody and chords together, so MySong's authors put it to the test, asking experienced musicians to rate its output on a scale of 1 to 10.

For comparison, they also rated the chord sequences generated by Band-in-a-Box and some that were generated manually (by musicians). To remove any bias, the tests were "blind" (the listeners didn't know whose chords they were listening to). As you might expect, the musicians got the highest ratings, but MySong ran a very close second place.

In many cases MySong's output was preferred over the chords written by humans, although it must be said that the musicians only had 5 minutes to write the chords to each song. Why not listen and judge for yourself by following the link at www.audio4fn.org

MySong is never going to be an automatic songwriter of number one hits. But it might achieve the more modest goal of enabling ordinary people, who could never write a song at all, to experience the fun of composing their own music.

You never know, as with any research it may be a stepping stone for something greater: that great compositional intelligence that is yet to come. Perhaps you might be one of the audio engineers who will help create it!