Computer Music: Musc 216
Isadora Tutorials: Step Sequencer

In this tutorial you will learn how to program a "step sequencer."A SEQUENCER is midi jargon for a kind of "recorder" for midi commands. Since each MIDI COMMAND consists of 2 or 3 numbers, it is very easy to record these sequence of numbers and then play them back, hence a SEQUENCER. A STEP SEQUENCER is a program which allows the user to play back the individual MIDI commands in a controlled way using a TRIGGER device such as a key on the computer keyboard. Every time you press the key the next SEQUENCE of numbers which is a MIDI COMMAND is sent out (played). Consequently, the user can control the TEMPO of the sequence, playing fast or slow as desired.


STEP 1: MIDI COMMANDS

There are no new MIDI COMMANDS associated with this tutorial. Please refer to earlier tutorials for NOTE ON and NOTE OFF commands.


STEP 2: Decide on a TUNE (song) you wish to play with your StepSequencer and then write down the KEY NUMBERS for the notes of that tune.

There are several tools available to help you do this including:

- Notes on the Keyboard gives you the letter name and MIDI Key Number of specific notes

- MidiKeys will play the keyboard notes of your tune

As you are figuring out the notes to your tune, write them down in order. The example we will use is "Twinkle, twinkle little star" :

Note
#
C3
60
C3
60
G3
67
G3
67
A3
68
A3
68
G3
67
F3
65
F3
65
E3
64
E3
64
D3
62
D3
62
C3
60

STEP 3: Open your current Project2Controller and ADD a new scene called, "StepSequence"

See previous tutorials if you do not remember how to add a new scene.


STEP 3: Add the Actors to the new StepSequence Scene

Here is the logic for the StepSequence Scene:

1. press a key (we will use the '=' key) and turn ON the first note (see the table in Step 2)

2. press the key again, turn OFF the last note played and turn ON the next note

3. repeat #2 until you reach the end of the list of notes, then start over with the 1st note

Add these actors to your new StepSequence scene:

Another group of actors should be added to this same scene which will turn OFF the current sounding note and then RESET the Integer Counter Actor back to #1. Specifically, add another Keyboard Watcher Actor and another Integer Counter actor and connect them to the above group like this:

The second Keyboard Watcher Actor should test for the SpaceBar, just like the AllNotesOff routine in an earlier tutorial.


STEP 4: Try it out!

If you have all the actors in your scene and have set the various parameter fields as shown above, your StepSequencer should work. Go ahead and press the '=' key and see if you can hear your tune play.


STEP 5: Troubleshooting (debugging)

1. Did you set the '=' key in the 1st Keyboard Watcher Actor and the Spacebar in the 2nd Keyboard Watcher Actor?

2. Check the various parameter fields CAREFULLY. They must be EXACTLY as shown this scene will not work.

3. Did you put "WRAP" in the MODE parameter field of the 1st Integer Counter Actor and "LIMIT" in the MODE parameter of the 2nd Integer Counter Actor?

4. If you scene still does not work, ask your Instructor for assistance.


STEP 6: Add a Comment to your Controls Window

Add a comment which will direct the user which key to press to activate the Step Sequencer. For example:


STEP 7: Save your work

When you complete this tutorial:

Save your Isadora file. You will want to keep the OLD Project2Controller file you created in the last tutorial. So you can either RENAME that file as something like Project2Controller.OLD, or you can name this new file something like Project2Controller.CURRENT. Which ever you decide to do, you should always keep the copies of your older tutorial files in case you "mess up" and have to start over again.

2. Save another copy of this file and call it Homework14.YourLastName. See the Class Schedule for specific details about submitting this Homework assignment.


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