Synth what is polyphony

In Rack , monophonic cables are actually just a special case of polyphonic cables, having just 1 channel. This means there is only one type of cable in Rack : polyphonic.

Zero-channel cables are also possible, which make modules think the cable is unpatched. Deep Synth should have no lowest note, so it assigns voices in a pseudo-Shepard tone way. No note should be strictly lower or higher than any other note; the oscillators should be moving both up and down on every transition.

I went into more detail in the previous post. Again, I prototyped it in Jupyter notebook. The graph shows the notes of a D minor 7th chord being added one at a time. There are 20 different notes in the final chord! The magic of Shepard tones is that there is no definite bottom note. This chord is root and all three inversions, open and closed voicing, all at once.

The tenor sings a fifth. Our alto sings a higher root, and finally the soprano sings the third. All is good in the chapel. Now lets change from a Imaj chord to a IV major. Two notes change in this case. The third goes up a half step and the fifth goes up a whole step. Again, this is not intrinsically bad. However, what if we want the two chords to play simultaneously. Something like this might happen if you play the two chords in a very reverberant room.

All the voices need to keep sounding. What is the solution? The solution is to add more people to the choir. Remember, the maximum number of voices is governed by how many people are in your choir. Give me two more people, synth voices.

The two new singers can sing the fourth and the sixth. While everyone sings we use every available voice. There is a synth analog to this. Do you remember your ADSR envelopes? Attack is how they start singing. Decay is how long they take to settle into a final volume. Sustain is how loud they sing the note after decaying. Release is how long they take to let the note fade to silence. Since every voice gets its own amplitude envelope, we can let one fade as another comes in.

Once those notes fade out we are free to start another note. This is how polyphony works. I also have to admit something. We will cover unison in a future lesson.

Unison is a subset of polyphony. In polyphony, every voice can sing a different pitch. With unison, in contrast, those voices only double each individual pitch. A brief example of unison will use our four voice choir again. Now lets add four more people and have them sing the same notes.

Unison is cool because no two singers are exactly alike. If they were then the choir would just sound louder. Due to slight variations in pitch, timing, and other variables we get different sonics. I will show you how to do it inside of two synths. Primer is the synth inside of Syntorial. I will begin by using Primer as our example. Being a training synth, Primer has a pretty simple interface. You can find its polyphony features at the bottom left. Primer has two relevant modes here.

Having explored the way monophonic and duophonic analogue keyboards work, Gordon Reid puts away his Minimoog and Odyssey and descends into the complex world of polyphonic synths to a flourish of complex jazz chords.

Ah, polyphony. You wouldn't think that there's much to it, would you? After all, we were all brought up with out-of-tune Edwardian pianos, Bontempi organs, five-string acoustic guitars, and whatever else lurked unloved behind the sofa in the living room. You hit a note You hit another note It must be the same on a synthesizer, yes?

Well, no, otherwise I wouldn't have asked. Before we can analyse and judge the various ways in which synthesizers have achieved polyphony, we had better understand precisely what 'polyphony' is.

So I'll let you into a secret right away Let's remind ourselves of what happens when, for example, you hit a strike a string within grandma's piano or pluck a string on an acoustic guitar. As we learned in the very first part of this series, the sound thus produced will have a characteristic tone determined by the nature of the string, and it will vibrate at a particular set of pitches determined by its length and tension.

Of course, this isn't the end of the story. Percussive instruments such as these are loudest at the start of a note and, unless damped, their sounds die away to silence over the course of several seconds. Furthermore, the note is brighter ie. In addition to this, many such sounds fluctuate in some way, exhibiting modulations such as vibrato.

Numerous other factors determine the exact sound produced, so it's both surprising and comforting to know that we can reduce these factors down to three major attributes for many simpler timbres. The first of these is the principal waveform, which provides both the initial tone and the pitch. The second and third are the changes in brightness and loudness as the note progresses. Given this, we can design a simple, monophonic synthesizer, as shown in Figure 1 above.

This has an oscillator that creates the basic waveform, a filter that controls the tone, and an amplifier that controls the loudness. It's a very elegant design and — if the oscillator offers at least two or three initial waveforms — it will produce a huge range of imitative and 'electronic' sounds. Correctly set up, it may even provide passable imitations of our hammered and plucked strings. Of course, by virtue of its single oscillator, the synthesizer in Figure 1 above is capable only of producing one pitch at any given moment.

Therefore, as I showed in Part 18 of this series SOS October , its response to multiple notes is to play just one at a time, as determined by the key priority see Figure 2, above. Clearly, no matter how many keys you press simultaneously, this can never be a polyphonic instrument. Let's now return to our initial consideration of a piano or acoustic guitar. Imagine that you play a single note — say, middle C — and listen to the way that it develops over time.

Initiating the second note does not affect the first So let's add more oscillators and more pitch CVs to the design in Figure 1.

Surely we've then done everything necessary to let us produce multiple instances of our imitation of the stretched string? In other words, we have designed a polyphonic synthesizer, haven't we? Unfortunately, no. This design see Figure 3, above has numerous flaws.

To understand the most important of these, remember that an analogue synthesizer's oscillators are always oscillating. On any commercial instrument, pressing a key on the keyboard may determine the pitch at which they do so, but it does not 'switch them on and off'. The amplifier at the end of the signal chain does this. Therefore, if the amplifier in Figure 3 is passing the sound of any one oscillator, it is passing the sound of all the others.