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Enchanting Instruments 110 - U-he Bazille Review Oscillator PD

2025-01-22

Theme:sound&person, sound

u-he / Bazille

Casio PD Sound Source (Phase Distortion)

This is about the PD sound source used in Bazille's four oscillators. There are many soft synths that use FM sound sources, but PD sound sources are in the minority. I think that this is a sound source that many people are not familiar with, so I would like to touch on the principles as well. u-he's president Urs Heckmann says that the first synth he bought was a Casio CZ-1000, so it seems that he has a lot of feelings for PD sound sources. When you use Bazille, you can feel that sentiment.

The lower half of the oscillator in Bazille has been extended with unique PD settings.

The History of PD Sound Sources

PD sound source is a digital sound source method that was first used in Casio's first synthesizer, the CZ-101, in 1984. Seven synthesizers with PD sound source were released by 1986. In 1988, PD sound source evolved into iPD sound source. However, in the 1990s, Casio also shifted to PCM sound source, and PD sound source ended. From 2000 onwards, we began to hear PD sound sources in software synthesizers, and Bazille is one such example. Although it is not a major sound source, its concept is still valid today. As a sound source that can create a variety of sounds from a single waveform, PD and FM sound sources may be popular with enthusiasts.

Casio CZ-101, CC BY-SA 4.0 (quoted from Wikipedia)

PD sound source is easier to use, like an analog synthesizer, compared to the difficult FM sound source. The FM sound source made it possible to create a wide variety of sounds, but because it was a completely different synthesis method from conventional synthesizers, I think there were many people who gave up on sound creation.

In contrast, the PD sound source aims to be a digital sound source that can be used like an analog synthesizer. I think that the fact that Isao Tomita was involved in the development stage was also a big factor. It seems that the principles and behavior were also pursued to be like analog synthesizers. The FM sound source of sine waves and the PD sound source of cosine waves seem like they are related, and there are also similarities in terms of mathematics because they are digital processes, but I get the impression that the concepts are completely different.

Principles of PD Sound Sources

In contrast to FM sound source sine waves, PD sound source is based on cosine waves. PD is an abbreviation for Phase Distortion. By distorting the phase angle when reading out the cosine waves stored in ROM, it is possible to create a variety of sounds. The following diagram shows how this works. The red cosine wave (minus) is the waveform stored in ROM, and this is distorted using the blue readout table to obtain the green output waveform.

If the readout table is y=x, that is, if it is read out sequentially, the output waveform will also be a cosine wave.

In the case of a sawtooth wave, the readout table instantly jumps to the center of the cosine. In this way, the second half of the wave becomes the output waveform, and you can easily create a sawtooth wave with a sharp edge, even if it is a little distorted. This is a part that is difficult to achieve with an FM sound source. The sample below is a soft pad sound that uses a sawtooth wave, which is difficult to achieve with FM.

Output Waveform that is Prepared in Advance for the PD Sound Source

The original PD sound source did not allow users to create sounds from cosine waves, but rather from eight types of pre-processed waveforms. In addition to basic waveforms, there were also waveforms that resembled the resonance of analog synthesizer filters. Compared to FM sound sources, it was a sound source that was easier to understand graphically and more intuitive. On the other hand, it was not a specification that could respond to the fanatical request to create from cosine waves. Bazille also has a similar waveform, but it has more flexible settings and you can create waveforms other than cosine waves. As for resonance, Bazille also has a feature called Fractalize that allows you to do the same thing. This also allows you to do strange things like nesting resonances.

The following are the eight waveforms included in Bazille's PD. They are slightly different from the Casio PD.

Morphing

It was possible to morph between the cosine wave and the output waveform. This has been carried over to Bazille. The following shows how morphing is used in Bazille. I think the reason why morphing has become easier to use is that it is a reproduction of analog synthesizers. It is probably the result of trying to reproduce analog synthesizer sounds with resonance digitally.

Let's try making the above into a sound. Since we're at it, let's make it sound like it's been through an analog circuit. Bazille is also an analog emulator, so the amount of distortion can be changed significantly by adjusting the levels, etc. Next, let's try making a resonance sound that sounds like an analog synthesizer, using only PD without using a filter.

Combination Waveform

One unique feature is that you can select and combine different waveforms for odd and even numbers. Depending on the combination, the octave pitch may become ambiguous, but this is a waveform that is only possible with digital technology, which is difficult to achieve with analog technology. The following are the waveforms and names of Bazille, so they are slightly different from the Casio PD.

PD Sound Source Expansion by Bazille

Bazille is an extension of the original PD sound source, and it is more flexible. The default sound is created from a cosine wave, but Bazille allows you to draw your own waveform using a map. The resolution is up to 128, and there is no interpolation, so you need to be careful how you use it. It can also be used in an additive way. The procedure is to adjust the level of each harmonic, and then convert it to a spectralize waveform. The figure below shows an example of a waveform that handles up to the sixth harmonic. I have also included the results of the oscilloscope and frequency spectrum.

Bazille Oscillator PD Sound Source Summary

As you can see, the PD sound source section of Bazille is a fairly faithful reproduction of the original Casio PD sound source. If you're creating something completely new as software, there's no need to be so close to the original, but Bazille has a clear original source, and you can feel the respect for each of them. u-he's latest synth, Zebralette3 (free), also has a function equivalent to the PD sound source built in, but this one is designed to be handled with complete freedom.

Next time, I will explain Bazille's semi-modular part.


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achapi

楽器メーカーで楽器開発していました。楽器は不思議な道具で、人間が生きていく上で、必要不可欠でもないのに、いつの時代も、たいへんな魅力を放っています。音楽そのものが、実用性という意味では摩訶不思議な立ち位置ですが、その音楽を奏でる楽器も、道具としては一風変わった存在なのです。そんな掴み所のない楽器について、作り手視点で、あれこれ書いていきたいと思います。
blog https://achapi2718.blogspot.com/
HP https://achapi.cloudfree.jp

u-he / Bazille 簡易パッケージ版

u-he

Bazille 簡易パッケージ版

¥18,700(incl. tax)

Virtual Instrument Plug-in, synthesizers, VST2 / AU / AAX

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