Many years ago, I created an article on the Hauptwerk 4 aliasing. It is still diplayed on my web. Many users are asking whether the audio engine improvements of the recent Hauptwerk versions are worth the upgrade. This article gives the answer. I prepared a pure sine wave at 2 kHz, roughly a middle b of a 2' stop, i.e. sound which is often used in pipe organs. I loaded this sine wave to Hauptwerk 4, Hauptwerk 6 and Hauptwerk 7 respectively, and observed the results of the audio processing.
The experiment tested how good Hauptwerk is in repitching tones. One would be tempted to say, that it is not a big concern, because there is little need of repitching anyway. Not quite so. Hauptwerk repitching algorithms are met on many occasions, let me try to enumerate them:
- 1.) when changing temperament (for example from equal to meantone)
- 2.) when changing pitch (for example to match the a=440Hz)
- 3.) when wind model is at work
- 4.) when random pitch error is at work
- 5.) when pipe coupling and pipe detuning functions are at work
- 6.) when the tremulant model is at work
Perhaps I forgot some other moments when pitch is being altered in Hauptwerk during performance. Anyway, repitching is almost always at work during performing in Hauptwerk. The quality of the repitching algorithm is decisive for the overall audio output quality.
With the 2kHz sine wave loaded, I performed manual repitching of the "pipe" by +50 cents, and then by -50 cents, using the slider present in Hauptwerk pipe voicing. I was recording the result to a wave file. Here the output:
Hauptwerk 4.2. As expected, the audible harmonic distortion and aliasing starts to happen already when the sine wave is repitched by +-10 cents, perhaps even earlier. That has always been a major problem in Hauptwerk 4.2, because it always spoiled the sound of the aliquotes, where this phenomenon was heard massively, introducing new out-of-tune "harmonics" to the sound completely unrelated to the played tones, also making the sound rather sharp and pungent.
- Attention! The pure sine wave is unpleasant to listen to! Attention during listening! Audio example (wav format for reference) recorded directly from Hauptwerk, no further manipulation.
Visualization (click the image to enlarge it) shows what we can hear: a lot of new "tones" (= lines) introduced all around (up and down) the original sine wave.
Hauptwerk 6, the same sine wave used for the experiment. First at the "standard" audio quality, which gives the result as Hauptwerk 4.2.
- Audio example (wav format for reference) recorded directly from Hauptwerk, no further manipulation. The last pitch reset done with the voicing "reset" button, therefore rather abrupt pitch shift at the end of the file.
Visualization (click the image to enlarge it) shows what we can hear: the audio quality of the pitch shifts is the same low as in Hauptwerk 4.2. No surprise, we are told that the "standard" audio quality is the same as the audio of Hauptwerk 4 in the user manual.
Hauptwerk 6, now using the "higher" audio quality setting. We can see that the hamonic distortion is far less audible, to be honest, I did not hear it at all during the test. But the visualization shows, that there is some minor distortion present in the audio. It is definitely far less obtrusive than the Hauptwerk 4.2 audio output.
- Audio example The audio example (wav format for reference), recorded directly from Hauptwerk, no further manipulation.
Visualization (click the image above to enlarge it) shows what we can hear: there are almost no additional "tones" around the 2kHz sine wave. The surrounding of the sine wave is almost pure night, i.e. silence. The vertical "spikes" are the moments when the pitch slider is being dragged, introducing some artifact at those very moments only. At least part of these spikes are artifacts of the tool converting the sound to the picture (due to the time "slicing"). Very good result, clear improvement over the Hauptwerk 4.2.
Hauptwerk 7, using the "higher" audio engine processing quality setting (Organ Preferences). This setting has three options: "lower" (we are told that this equals to the Hauptwerk 4.2 quality), "medium" (we are told that it would equal to the Hauptwerk 6 "higher" quality), and the new "higher" option, which we tested. I heard no audible distortion or aliasing when testing. Also, the visualization shows that the new "tones" introduced are almost invisible, i.e. almost absent, even less prominent than what we have seen in Hauptwerk 6. So, it has been proven by this experiment, that the quality of the audio processing in Hauptwerk 6, and Hauptwerk 7, is a huge audible improvement over the older Hauptwerk 4.2 version.
- Audio example (wav format for reference), no further manipulation.
Visualization (click to enlarge) shows what we can hear: almost no visible distortion or aliasing.
Finally, Hauptwerk 6 (left) and Haptwerk 7 (right) results seen side by side, for a direct comparison. The spectrum is zoomed for a clear vision of the area around the 2 kHz.
In this experiment, I only tested the audio engine processing quality in pitch shifting, which is decisive for the overall audio quality in Hauptwerk. I did not test the new higher quality processing of the Hauptwerk models (wind model, tremulant model, etc.) which can probably bring even further improvements in the resulting audio.