museline: charting melodic contours via web service
In the last post, I mentioned I was playing with Google App Engine and Google Chart Tools.
Last night, with some silly movie streaming in the background, I was in bed tinkering with a little idea that I'm sure has been done a-thousand times already and that may be built into high end music notation applications. But it hasn't been done by anyone as stoopid as me!
What I did was whip up a little App Engine/Python app where one can pass it a partwise MusicXML file and it will use Google Chart Tools to create a little line chart of the melodic contour of the first <part> element.
Here's a screenshot below of the results using the MusicXML sample file available on the MakeMusic site of Schumann's "Im wunderschönen Monat Mai" from the Dichterliebe. The app has an "mxml" parameter that tells it which MusicXML file to use a la "http://localhost:8083/?mxml=http://downloads2.makemusic.com/musicxml/Dichterliebe01.xml".
I've embedded a really nice performance on YouTube if anyone wants to follow along. The contour graph represents the vocal part only.
Now, this is just a start. There's a lot of work to do if I pursue this. For starters, I'd like to make the chart synced with an audio/video recording. I don't know if I can do that with Chart Tools, but probably with the <canvas> element if nothing else. Also, I haven't tried this yet with any non-homophonic parts. Anyway, it's a start and it's kinda fun.
I tried to add another line for the actual pitch class contour but it wasn't as interesting to look at as the melodic contour so I disabled that "feature". By pitch class, I mean I was using octave equivalency so that all "C" notes, for example, were plotted at the exact same vertical position as opposed to the screenshot above where two "C" notes an octave apart would have different vertical points on the graph to depict the intervallic difference.
As far as plotting the notes, I ignored rests and durations. I just plotted the pitches as below, starting with "C" with a value of "1" and with the "B" a seventh up from that "C" receiving a "12".
- C : 1
- D : 3
- E : 5
- F : 6
- G : 8
- A : 10
- B : 12
This way a "C-sharp" and "D-flat" receive a score of "2", for example, because they lie between "C as 1" and "D as 3".
In MusicXML, the <step> element has the note name and the optional <alter> element, which is a number, tells you if it's sharp or flat, etc. The numerical <octave> element tells you what octave range the pitch is in.
So what I'm doing is pulling out the <step> value and converting it to a number as above, adding the <alter> value (a flat is a negative number), and then
multiplying adding that sum to 12 times the <octave> value. Then, I multiple the value by ".01" just to reduce the number because I want the graph's vertical limit to be a small number even though this shouldn't change the contour itself.
Last, I'm trying to pull some basic descriptive metadata if they are present in the MusicXML file and show it below the graph.
Maybe I'll do more with this later. Just goofin' for now.--------------