Percussion in MusicXML
Percussion instruments can be either pitched or unpitched. Percussion instruments with definite pitch, such as timpani or mallet instruments, are handled as using normal musical notation.
When the instrument has no definite pitch, like a bass drum or snare drum, notation gets stretched. The use of vertical space to represent pitch instead is used to represent different instruments. Yet sometimes we have more percussion instruments handled by one player than can fit into the lines on a staff. In other cases, we may have only one unpitched instrument to notate, where the vertical space on a 5-line staff would be wasted.
MusicXML allows percussion music to be represented both as heard and as notated by use of several features:
- Representing unpitched instruments visually by specifying placement on the staff.
- As with tablature, staves may be more or less than 5 lines high.
- Specifying multiple instruments per part
- Specifying the MIDI playback for each instrument (for instance, by a single MIDI pitch in a percussion kit).
- Alternate notehead shapes let multiple instruments to share a single line on the staff.
Unpitched Notes
To illustrate MusicXML's percussion features, here's a two-bar example for two players: one on a drum kit, and one on cowbell:
In the drum part, the top space (B in bass clef) is used for the cymbal (diamond notehead) and hi-hat (x notehead). The E space is used for the snare drum, and the bottom A space is used for the bass drum. The cowbell player has only one instrument, so it is represented on a one-line staff.
Since these notes have no definite pitch, it would be misleading to represent them using the pitch element. An analysis program looking for a series of repeated B's should not return this piece of music. Nor should a program looking for a series of repeated F-sharps, based on the General MIDI pitch for a closed hi-hat.
Instead, we represent percussion and other unpitched instruments with the unpitched element. As with rests, there are display-step and display-octave elements to indicate where the note should appear on the staff, based on the current clef. So the cymbal and hi-hat notes on this bass clef staff are represented as:
<unpitched>
<display-step>B</display-step>
<display-octave>3</display-octave>
</unpitched>
Percussion clef is treated like treble clef when determining the display-step and display-octave. So if this part had been notated in percussion clef instead of bass clef, the resulting MusicXML would be:
<unpitched>
<display-step>G</display-step>
<display-octave>5</display-octave>
</unpitched>
Staff Lines
The cowbell part is an example where one player has one instrument, so the part is notated on one line both for clarity and saving space. The single line is specified within the attributes element for the part:
<attributes>
<divisions>1</divisions>
<key>
<fifths>0</fifths>
<mode>major</mode>
</key>
<time symbol="common">
<beats>4</beats>
<beat-type>4</beat-type>
</time>
<clef>
<sign>Percussion</sign>
</clef>
<staff-details>
<staff-lines>1</staff-lines>
</staff-details>
</attributes>
How do we determine the display-step and display-octave for a one-line staff? Since the percussion clef is treated like a treble clef, the G in octave 4 is on the second line of the staff. For this one-line staff, that G is one imaginary line above the staff (for a 2-line staff, it's the top line, and the middle line on a 3-line staff). Therefore the unpitched elements for the cowbell part are:
<unpitched>
<display-step>E</display-step>
<display-octave>4</display-octave>
</unpitched>
Multiple Instruments Per Part
Percussion parts are one case of many where multiple instruments are sharing the same part. This is represented in MusicXML by including more than one score-instrument element within a score-part. Each note can then contain an instrument element that refers back to the id of the score-instrument. Note that the score-instrument id must be unique throughout the entire piece. Two score-part elements cannot each have a score-instrument element with the same id.
To represent MIDI playback for each instrument, we add a midi-instrument element for each score-instrument. In this case, we are using a General MIDI instrument, so we include a midi-channel of 10 for each instrument. We then use the midi-unpitched element to indicate the MIDI pitch that corresponds to a particular sound in a General MIDI drum kit.
The part-list for our two-bar example looks like this:
<part-list>
<score-part id="P1">
<part-name>Drums</part-name>
<score-instrument id="P1-X2">
<instrument-name>Bass Drum</instrument-name>
</score-instrument>
<score-instrument id="P1-X4">
<instrument-name>Snare</instrument-name>
</score-instrument>
<score-instrument id="P1-X6">
<instrument-name>Hi-Hat Closed</instrument-name>
</score-instrument>
<score-instrument id="P1-X13">
<instrument-name>Crash</instrument-name>
</score-instrument>
<midi-instrument id="P1-X2">
<midi-channel>10</midi-channel>
<midi-program>1</midi-program>
<midi-unpitched>37</midi-unpitched>
</midi-instrument>
<midi-instrument id="P1-X4">
<midi-channel>10</midi-channel>
<midi-program>1</midi-program>
<midi-unpitched>39</midi-unpitched>
</midi-instrument>
<midi-instrument id="P1-X6">
<midi-channel>10</midi-channel>
<midi-program>1</midi-program>
<midi-unpitched>43</midi-unpitched>
</midi-instrument>
<midi-instrument id="P1-X13">
<midi-channel>10</midi-channel>
<midi-program>1</midi-program>
<midi-unpitched>50</midi-unpitched>
</midi-instrument>
</score-part>
<score-part id="P2">
<part-name>Cowbell</part-name>
<score-instrument id="P2-X1">
<instrument-name>Cowbell</instrument-name>
</score-instrument>
<midi-instrument id="P2-X1">
<midi-channel>10</midi-channel>
<midi-program>1</midi-program>
<midi-unpitched>57</midi-unpitched>
</midi-instrument>
</score-part>
</part-list>
Each note then includes an unpitched element to show where the note is on the staff, and an instrument element to indicate which instrument is used and how to play it back using MIDI. The first bass drum note looks like this:
<note>
<unpitched>
<display-step>F</display-step>
<display-octave>4</display-octave>
</unpitched>
<duration>2</duration>
<instrument id="P1-X2"/>
<voice>2</voice>
<type>quarter</type>
<stem>down</stem>
</note>
Our Dolet for Finale plug-in creates these instrument names like "P1-X2" to make it easy to generate unique names for each score instrument. It would be better to use more readable names that are still unique across the entire piece.
Notehead Shapes
The one remaining task is to specify the alternate noteheads that distinguish the hi-hat from the cymbal. While the MusicXML playback can distinguish these by the use of different instruments, a drummer will certainly appreciate having different notehead shapes for different instrument on the same line.
The MusicXML notehead element specifies these different shapes. Standard values include slash, triangle, diamond, square, cross, x, circle-x, normal, and none. Enclosed shapes like normal, diamond, triangle, and square can use the filled attribute to indicate a filled or hollow shape. The first two notes of the cymbal/hi-hat line look like this:
<note>
<unpitched>
<display-step>B</display-step>
<display-octave>3</display-octave>
</unpitched>
<duration>1</duration>
<instrument id="P1-X13"/>
<voice>1</voice>
<type>eighth</type>
<stem>up</stem>
<notehead filled="no">diamond</notehead>
<beam number="1">begin</beam>
</note>
<note>
<unpitched>
<display-step>B</display-step>
<display-octave>3</display-octave>
</unpitched>
<duration>1</duration>
<instrument id="P1-X6"/>
<voice>1</voice>
<type>eighth</type>
<stem>up</stem>
<notehead>x</notehead>
<beam number="1">continue</beam>
</note>
The filled attribute on the notehead element is also useful for multi-part piano music. There are many cases where, for instance, a downstem half note shares a hollow notehead with an upstem eighth note. The eighth note can specify that it uses an unfilled normal notehead, making things display correctly when moving back and forth between notation programs.
Measure Styles
Our cowbell part also shows the use of a one-bar repeat symbol. This and similar repeats and multimeasure rests are represented using the measure-style element. The music in the second bar should be specified just as in the first bar (four notes with display-step E, display-octave 4, and instrument P2-X1). At the start of the bar, we indicate the beginning of the one-measure repeat style:
<measure number="2">
<attributes>
<measure-style>
<measure-repeat type="start">1</measure-repeat>
</measure-style>
</attributes>
Further details about the measure-style element can be found in the attributes.dtd file.
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Last updated January 2, 2008.