Build A MIDI Synthesizer Tutorial Question

Getting Started
1

Hi,
I’m going through the Build A MIDI Synthesizer tutorial and I ran upon this piece of code:

        for (auto i = 0; i < 4; ++i)                // [1]
            synth.addVoice (new SineWaveVoice());

The footnote for it says:
* [1] : We add some voices to our synthesiser. This number of voices added determines the polyphony of the synthesiser.

Regardless of what I change the ‘4’ to, the synthesizer still has 6 note polyphony. I’d like to get more if possible. (Yes, I did rebuild and even cleaned the build folder after changing it just in case). Any insights from experienced polyphoners?

Thanks,
Matt

2

How are you testing the synth? Where do the MIDI notes come from?

3

Through the computer keyboard using the synthesizer class in the tutorial.

Matt

4

Computer keyboards typically have limits on how many keys can be pressed simultaneously. You should test with a proper MIDI keyboard instead.

5

Fair enough. But if I lower the number to ‘2’ instead of 4, it can still play 6 notes.

A correction to my above comment. The keyboard is implemented using the midiKeyboardComponent.

Thanks,
Matt

6

The keyboard component shows the notes it itself has received, the polyphony you set for the synth object isn’t connected to that.

7

But if the keyboard component receives 6 notes, and sends it to the synth object, if the synth object is set for 4 notes (as in the for loop), how can the synth play all 6 notes? Something isn’t mathing for me.

Matt

8

The synth steals voices (turns off already playing ones) when you try to play more notes than the available polyphony.

9

Ok. You’re right. I wasn’t listening properly (flashback to elementary school). I changed the for loop to 1 and it only played one note at a time. The keyboard component was still showing multiple keys. I understand that’s the limitation of/issue with the keyboard component. The six key limit I also understand seems to be the limit of my computer keyboard. I’ll plug in a real MIDI keyboard and test further.

THANK YOU for the explanation and the patience with my simple questions. :slight_smile:

Matt