The sixtyforgan: Commodore 64 equipped with a spring reverb | Hacker News Reader

The sixtyforgan: Commodore 64 equipped with a spring reverb

linusakesson.net

215 pointssohkamyung46 comments

This is super-cool, and the multi-part recordings really show off what's possible with this creation. As someone who works on pipe organs (including their voicing and tonal finishing) for a living, I do want to comment on his statement that "at least in theory, organ pipes produce very simple waveforms". Actually, in both theory and practice they produce a huge range of overtones in addition to the fundamental, with open pipes being capable of producing both even and odd partials while stopped pipes produce only odd partials. While it's possible to construct and voice pipes in a way that comes close to producing only fundamental, it's almost never the goal, the exception being some pedal stops that are intended to produce shake (a sine wave of very low pitch) in the room and minimal color (overtones). Instead, we usually aim to give each stop its own complex and refined tonality consisting of huge numbers of harmonics, the profiles of which are dictated by both the construction and materials of the pipe and the process of voicing (the very delicate manipulation of numerous parts of the pipe to change its color and speech characteristics). Having said that, he's absolutely right that a good acoustic helps make a good instrument -- there's a saying that "the room is half of the organ"!

Maybe simple envelopes would be more accurate. Any waveform played with a rectangular envelope will sound "organy." Add modulation and a more nuanced envelope to avoid this.

Yes, electronic organs often have rectangular envelopes. Pipe speech has an envelope that is far more complex than one might expect; indeed, one of the goals of voicing is to impart an envelope that allows the pipe to be "articulate", to a degree dependent on the caracteristics of the stop of which it is a member and depending on the overall tonal milieu of the specific instrument. Taken to its extreme, this results in a clunky "chiff" sound at the start of each note, something often heard in instruments designed in the "American Classic" and "Neo-Baroque" styles; but with more refinement, it can produce the gentle puff at the beginning of a flute note, or the "bubble" articulation of a French Horn. And at the other end of the envelope is a characteristic decay, initiated by the closing of the valve beneath the pipe and sustained by the resonance of the pipe body (which, in large pipes, can go on for several seconds).

I didn't know the term "chiff," but looking up videos of the sound, it's very similar to an effect I accidentally created in a recent digital synthesis project by using a low sample rate for the envelope (2kHz). I think the stair-stepped shape of the attack created some inharmonics in the audio.

Is chiff the result of inharmonics created by brief turbulence in the airflow?

Yes indeed. In extreme cases, it can give the impression of a xylophone! To control chiff, we use a pointy double-sided knife called a "nicking tool" to create a series of evenly-spaced nicks across the entire width of the flue (which is the slot at the base of the mouth, formed by the lower lip and the languid inside the pipe; air leaving the foot of the pipe is focused by the flue on its way towards the upper lip). Often the nicks are cut into both the lower lip and the languid at similar depths and perpendicular to the flue, although there are exceptions; the width, depth, and spacing of the nicks all have tonal implications. Care must be taken to avoid over-nicking, as the articulation -- some of which is necessary even when chiffing is not desired, and which may need to be more prominent when close to the pipe than when listening from the room -- can be completely lost.

Fascinating. This is the most scientific explanation of nicking that I could find:

http://www.colinpykett.org.uk/physics-of-voicing-organ-flue-...

I think the OP means "simple waveforms" in terms of the ubiquity of square wave oscillators, not simple in the sense of being a pure sine wave.

Wondering whether there is any Organ Dubstep.

I've always heard this as somewhat organ-y: https://youtu.be/uuxOGtAE1Io

But it's

a) almost certainly synth based

b) much closer to a WEM-like desktop organ than a church organ

Your point was more about the sub frequency shaking, right? Nothing like that comes to mind.

Yes, was thinking about the sub bass that is possible with church organs.

I love the crazy mechanical stuff they came up with before solid state analog electronics matured enough to supplant them.

Spring and plate reverbs, oilcan delays and tremolos, tape recorder based delays and other crazy rube goldberg contraptions which could produce some amazing sounds.

It's amazing--I love the story of Delia Derbyshire creating the iconic theme for Dr. Who using tape loops and all kinds of wacky tech: https://www.youtube.com/watch?v=xkIEkLww3lg

The story behind the famous TARDIS sound and Daleks voices is also worth mentioning.

https://www.radiotimes.com/tv/sci-fi/interview-doctor-whos-b...

A broken piano and a ring modulator... those were the days!

I'm still not sure a normal desktop would be enough to compute as many paths as that spring tank did. How would you do it solid state analog?

I was mainly thinking of when CCD bucket-brigade type devices came along.

The standard (digital) approach these days is a convolution reverb which take an impulse response of a space (a cathedral or room or what not) and then apply it to the signal.

My favorite is the Leslie: https://en.m.wikipedia.org/wiki/Leslie_speaker

Those are great. I played in a group with an organ player who had a B3 into a leslie. I could just sit there watch the speaker horns whir around. They made a pretty good breeze too.

I got to see Booker T. Jones (of Booker T & the M.G.'s) and his B3-into-dual-Leslies setup at a show a few years back. It was awesome. That man put on a helluva show.

https://x42-plugins.com/x42/x42-whirl

"x42-whirl is designed to imitate the sound and properties of the electromechanical rotating speaker device that brought world-wide fame to the name and products of Don Leslie. It is a standalone version of the effect that came to be with the setBfree synth. Rather than simulating the net effect of the electromechanical device, x42-whirl physically models the properties, which results in very accurate representation of the sound of the real device. Since all individual parts are modelled, x42-whirl not only provides advanced control, but also facilitates customizations, some of which are not feasible in the mechanical device."

The Mellotron is the most complicated example of this I'm aware of. Individual tapes for every key: https://en.wikipedia.org/wiki/Mellotron#/media/File:Changing...

https://en.wikipedia.org/wiki/Mellotron

Here's something similar that you might be interested in: https://www.youtube.com/watch?v=NmGaXEmfTIo

I should have mentioned that it's a Mellotron in the intro for the Beatle's Strawberry Fields.

What's funny is a lot of people spend a lot of money chasing those same plate and spring reverb tones in digital pedals and effect modelers. We never would have come up with those iconic tones without the limitations of the technology! Personally I think the pure digital modelers can do much nicer reverbs but if you want to play surf music, its got to be a drippy spring.

Does anybody know of recent-ish software or hardware projects that implements the live note-level (pre-synthesis) manipulation seen in lft's amazing "bitbuf"[1] device? In the presentation video[2] at 3:26, lft describes how the "bass tracks" are "transposable". After entering a bass part in the key of C, playing single notes transposes the note values up to that key (i.e. playing D transposes all note values in the bass part by +2 semitones). This type of transformation happening live, at the MIDI/note level is the goal.

Sunvox[3] can do something similar using pre-defined arps in a metasynth, but Sunvox is primarily a tracker, and isn't really focused on playing live. In an ideal world, I want to be able to do live loop recording/overdubbing akin to my Line6 DL4, but at the MIDI/note level where the entire loop can transpose as needed (or even harmonically transform to a new chord?! whatever that means?)

lft's "bitbuf" hits a really unique - and mostly unexplored - idea of live MIDI transformation, where existing loop information doesn't have to be static...

[1] https://www.linusakesson.net/bitbuf/index.php

[2] ibid, lft_bitbuf_presentation.avi

[3] https://warmplace.ru/soft/sunvox

This is very reminiscent of Wendy Carlos's "Switched on Bach". If you liked the video, but have never heard the album, I recommend you track down a copy. Tragically it never seems to be available on streaming services (at least the ones I subscribe to).

Anna von Hausswolff has done some great work with real church organs too.

It's International Trans day of Visibility, and if you, for some reason; haven't checkout Wendy Carlos' work yet, first - you're missing out - and, secondly, it's a great excuse to do so.

Switched-on Bach is phenomenal, and obviously the Clockwork Orange OST is just something else. :)

Happy to see Anna von Hausswolff mentioned here! Dead Magic is such a great album.

>Tragically it never seems to be available on streaming services

It appears to be on archive.org: https://archive.org/details/tntvillage_541011/Switched+On+Ba...

Used an old late 80s/early 90s 16-channel Yamaha mixer that had a spring reverb. We used to take it on the road for live mixing. If it got bumped just right, any channel with the reverb through an open send would make the most horrifying noise. After the first time, your hands would immediately reach for the send knob to kill it, but it would take minutes for the spring to settle down again.

Growing up my siblings and I made the same discovery about an old organ my parents had. The first time it happened we were scared to death -- it basically sounded like metallic thunder. But after that we would trigger it on purpose by jumping up and down or just tapping on the organ itself.

What a madlad! Really appreciate the in-depth knowledge he developed to make this.

Keep looking! Linus Åkesson (AKA "LFT") has done A LOT of mind blowing things.

Writing code for the Demoscene? Not good enough. He made his own hardware to run his own demos: http://www.linusakesson.net/scene/craft/index.php

His research into why not all C64's are created equal (and provided a software work around to a hardware flaw) lead to being able to do safe high speed full screen scrolling. And he did it looking at someone else's logic analyzer dump!

http://www.linusakesson.net/scene/safevsp/index.php

His 256b C64 intro "A Mind Is Born" was also on HN recently: https://news.ycombinator.com/item?id=26511266

He was also involved in creating the Teenage Engineering OP-1 and pocket operator synthesizers.

Looked at the other pages on that site as well. I am floored, Linus Akesson absolutely rocks.

> [..] the reason church organs don't sound like chiptunes is primarily because of the acoustics of the church."

Another reason is that arpeggiated chords are a big part of what makes a chiptune sound. Can't do that on a real church organ, air has inertia, latency and attack time are significant. Also fingers hurt after while. Not so with a SID and a small broadband speaker.

If you want to get some idea of recent SID creations, this song came last night and blew my mind:

https://csdb.dk/release/?id=202283

Preferably play it on a 12v SID full blast on speakers!

Amigans find a nice little easter egg in the first video :)

yeah this really gave my brain a shiver of pleasure

That's right! It really loved that little Amiga Basic program and studied how it made the church organ timbres (along with the plot lines).

What easter egg? I remember my Amiga doing the same thing soundwiseish but that was 8bit digital 4 channel stereo sound on a 68k that could do the reverb in software. This is a simple waveform generating SID chip which is what makes it cool. In other words I missed any bit of Amiga easter egg.

Spoiler alert - this video shows it all: https://youtu.be/522uWGQV134?t=28

Compare to the first video on the site, at about 4:07

Ah, thanks. I wasn't certain that the C-64 or any other computer at the time that could make sounds didn't have the same little demo program. I guess the choice of music paired with the visual explains the flashbacks. As far as I know the C-64 had the same program first, Amiga did it better, and this part of the video was an homage to some old C-64 demo that I wouldn't know about.

The visual effect was common on any computer that had pixels instead of just 80x24 blocks. The music (however generated) was always some bit of very classical recognizable by almost anybody so especially church music. The same sort of little demo program was on everything that could pull it off.

I was looking for a logo or a window or something else not so tenuous.

It's awesome how the spring reverb is a sneaky way to somewhat simulate polyphony beyond 3 voices.

Also checkout the chipophone, Linus Åkesson rocks

Really excellent!

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