Xx Tutorial 3: Using the Canon Tool By Len Sasso and Eric Wenger

Xx provides interactive tools for composing Canons. A Canon consists of several voices playing the same theme which is offset in time and in pitch. Typically, the first voice enters at the fundamental, and the second voice enters a fifth or an octave higher and a half or whole measure later.

In our example, we are going to compose a canon starting with two voices and ending with three.

Step 1: Set up the scale, instruments and tempo.

XX provides key and mode constraints for entering and manipulating notes. So, before we start, we need to decide upon a key. Use the Mode menu to choose the MinorNatural scale in the key of E.
Set the tempo to 88 BPM.

For generalizability, we have used the Beatnik software synthesizer General MIDI instrument. If you have better sounding MIDI instruments, please select the corresponding devices and program changes in the Track Set-up dialog.

The layout should be as follows:

• Slow string (program change 49) for tracks 1 & 2
• Ensemble string (program change 48) for track 3.
• French Horn (program change 60) for track 4.
  

Step 2: Set up the Canon tools

• A. Double-click the 2-Voice Canon icon to set up the  two voice canon parameters. In the 2-voice sections of our piece, we will have the second voice a fifth plus an octave (i.e. a 12th) above the first.
  
  
  

  The time offset (delay between each voice) is set to 480 which corresponds to a half note at 240 ticks per quarter. The dialog should look like the following picture:
  
  The "avoid dissonances" check box is turned off to prevent Xx from automatically “fixing” notes.

  In the main window, turn on the Display Octaves toggle so you can see the piece's notes 'shadowed' in each octave. This makes detection of dissonance easier.

  The grid is set to 120 (i.e. 8th notes).
  

Now we are ready to start.

Step 3: Composing section A

The first part will be a slow movement using only two voices, tracks 1 and 2.

• A. Select track one (orange) by clicking on the track box. This track will be used to enter the first voice.
  
• B. Select the 2-Voice Canon tool.
  
  We will start the piece with the fundamental, E. Click and drag on the E3 line to enter a whole note. Observe how notes on track 2 are automatically echoed with the proper pitch shift and time delay.
  

• C. Enter more notes with the mouse, trying to avoid dissonance.
  
  In the provided example, I started with whole notes (960 ticks) up until measure 5 then alternated half notes (480 ticks) and whole notes to create an offset rhythm. Beginning at measure 11, I mixed quarter notes (240 ticks), half notes and whole notes. The 480 tick offset makes interesting rhythmic juxtapositions when the 240, 240, 480 overlay the 480, 240, 240 on the other track.

  Tips: if a note is not pleasing, you can use the arrow keys to transpose it before entering any more notes. The corresponding note(s) in the other track(s) will follow. You can also modify notes you entered earlier by clicking and dragging them. (Make sure the cursor has changed to a four-way arrow before doing this. This cursor indicates that you are exactly over the note.) To maintain consistency in the canon, only notes in voice 1 should be modified in this way. (Note: To modify an individual note without changing the corresponding note in the other voice, use the pen tool.)
  

The first section will end up on the fifth, B. The end of voice 2 was fixed manually to conclude both voices at the same time.

Step 4: Composing section B

The second section will employ faster melodic movement using 3 voices. The difficulty is increased when composing canons with 3 voices since the overlapping of delayed and transposed melodies does not necessarily yield harmonious juxtapositions. Xx shows all voices as they are entered. This allows you to see harmonic relationships and tweak the canon accordingly.

• A. Double-click the 3-Voice Canon icon to set up the 3-voice canon parameters. In the 3-voice section of the piece,  we will have each voice a fifth above the previous one. (For example, if you enter E4 in voice 1 then Xx will enter B4 in voice 2 and F#5 in voice 3.) Change the Time Offset to 960 ticks (whole notes).
  

  
  

• B. Select the first voice by clicking on the green  track box. This track will be used to enter the first voice of the canon in the new section. The second voice will be entered on the next track (blue) and the third voice will be entered on the one after that (pink).
  
  • The first voice (track 2) is the Slow string instrument.
    The second voice (track 3) is the Ensemble string instrument.
    The third voice (track 4) is the French horn instrument.
    
• C. Start by entering an E4 at measure 19. Enter the notes for the 3-voice canon using different note lengths. Observe how notes on tracks 2 & 3 are automatically echoed using the proper pitch shift and time delay. In the example, I chose the following repeating form: 1 long note, 4 short and 4 medium (in ticks: 480 120 120 120 120 240 240 240 240).
  
  

  
  

Step 5: Fine Tuning

• A: Let's end the canon with a second, short theme at measure 25 using a different rhythm. (I chose: 1 medium length note, 2 long, 1 medium, 2 long). There is less freedom for choosing consonant notes because of the existing notes in voices 2 and 3. In the example, I entered two more measures to end on the fundamental, E, with a whole note at measure 27.
  
  

• B: Naturally, the later voices of a canon will end later than the first voice. In the example, I edited the duration of the final notes in each voice so that all voices end at the same time. (Control-option click on a note to change its length.)
  
  

• C: You can enrich a canon by adding short “sub-canons” at various points.
  In the example, I added more notes using the 3-Voice Canon tool at measure 23. I echoed existing patterns to fill in a logical gap. For shorter notes, to get a more "staccato" effect, I set the grid to 60.

  
  
  
  
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