Nate's Blog

Welcome back. This is part II of my python midi series. Part I can be found here.

Last time we set up our python program to successfully send a midi stream to our midi player.

Today we're going to loop a basic chord progression, and add some texture. Again, my midi player is Ableton Live, but this will work for anything that takes midi input.

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Writing Chords -

We're going to start with some basic minor and major triads - the root, the third and the fifth. The major third is 2 whole steps up from the root - 4 steps - and the minor third is a whole and a half step up from the root - 3 steps.

First, our function setup -

1
2import mido
3from time import sleep
4 
5def note(note,velocity = 64, time = 2):
6    return mido.Message('note_on',note=note,velocity = velocity, time=time)
7
8def note_off(note,velocity = 64, time=2):
9    return mido.Message('note_off',note=note,velocity = velocity, time=time)
10
11outport = mido.open_output('IAC Driver pioneer')
12
13def majorChord(root, duration):
14    outport.send(note(root))
15    outport.send(note(root+4))
16    outport.send(note(root+7))
17    sleep(duration)
18    outport.send(note_off(root))
19    outport.send(note_off(root+4))
20    outport.send(note_off(root+7))
21
22def minorChord(root ,duration):
23    outport.send(note(root))
24    outport.send(note(root+3))
25    outport.send(note(root+7))
26    sleep(duration)
27    outport.send(note_off(root))
28    outport.send(note_off(root+3))
29    outport.send(note_off(root+7))
python

The note method returns a mido.Message object that is sent to the port.

The majorChord and minorChord functions take in their root note, but also a duration argument. These functions play the chord, sleep for the duration, and then turn off the notes by triggering 'note_off' messages.

With this, we can loop a nice chord progression like so -

1C = 60 
2G = 55 
3A = 57 
4F = 53 
5
6while True:
7    majorChord(C,1)
8    majorChord(G,1)
9    minorChord(A,1)
10    majorChord(F,1)
11    majorChord(F,1)
12    majorChord(G,1)
13    majorChord(C,2)
python

Tada! we have a chord progression! It sounds a bit dull, though, so let's add some texture.

<iframe width="75%" height="265" src="https://clyp.it/2dtqyn41/widget" frameborder="0"></iframe>

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Adding Texture -

We're going to make two changes to make this progression sound less robotic. First, in our note generation, we've added a velocity modification variable. With every note generated, the velocity is now anywhere, randomly, between 44 and 84. This changes the intensity of the note.

In addition, we've added a pause function, which inserts of sleep of anywhere between 0 and .05 seconds. We've added this pause between the individual notes on the chord, everyso slightly staggering the notes.

1
2def note(note,velocity = 64, time = 2):
3    velocity_modification = randint(-20,20)
4    return mido.Message('note_on',note=note,velocity = velocity + velocity_modification, time=time)
5
6def note_off(note,velocity = 64, time=2):
7    return mido.Message('note_off',note=note,velocity = velocity, time=time)
8
9def pause():
10    sleep(randint(0,100) * .0005)
11
12def majorChord(root ,duration):
13    outport.send(note(root))
14    pause()
15    outport.send(note(root+4))
16    pause()
17    outport.send(note(root+7))
18    pause()
19    sleep(duration)
20    outport.send(note_off(root))
21    outport.send(note_off(root+4))
22    outport.send(note_off(root+7))
23
24def minorChord(root ,duration):
25    outport.send(note(root))
26    pause()
27    outport.send(note(root+3))
28    pause()
29    outport.send(note(root+7))
30    sleep(duration) 
31    outport.send(note_off(root))
32    outport.send(note_off(root+4))
33    outport.send(note_off(root+7))
python

And here is the output.

<iframe width="75%" height="265" src="https://clyp.it/g54lv0zg/widget" frameborder="0"></iframe>

You can hear how much more organic it sounds. Each loop is unique in its velocity and stagger values.

Thanks for reading. Stay tuned for more python midi projects!