Why are organs so easy to synthesize?

[ZeeOne]

It seems of all "real instrument" sounds, the easiest to create without the use of any sampling are organ sounds. Pipe organs, electric organs, etc...they sound very spot-on to my ears. Strings and brass retain an electronic flavor and plucked instrument sounds (such as guitars) always sound...well, terrible, if you ask me. But organs come out right.

Why is this?

The very fact that I'm evening asking this probably shows how little understanding of synthesis I actually have...

[Automatic Gainsay]

Many popular organ sounds can be created by stacking sine waves. In addition to that, organs traditionally have an on/off articulation.

[zmd]

The playing method is typically the same as well. guitars/violins/horns/etc have a very accidental interface, whereas keyboards are very deliberate.

[GuyaGuy]

The playing method is typically the same as well. guitars/violins/horns/etc have a very accidental interface, whereas keyboards are very deliberate.

You mean accidental like a saxophone reed accidentally being clamped to a mouthpiece and the randomly drilled holes that produce different tones when plugged with keys that just happen to be the same size?

Many popular organ sounds can be created by stacking sine waves. In addition to that, organs traditionally have an on/off articulation.

Organs also often try to emulate other instruments which make the results end up sounding similar. Or, in other words, a keyboard emulating another keyboard emulating flutes proves to be a pretty easy emulation.

[meatballfulton]

Pipe organs use pipes (doh) which are either closed or open. The pitch of the pipe is denoted by the length of the pipe in feet, which is why synth oscillator octave switches are usually marked in feet as well: 32, 16, 8, 4, 1.

Here is a link to the basic physics behind pipes. As noted in that link, closed pipes have odd harmonics only (square wave!) and open pipes have all harmonics (sawtooth!).

So how do pipe organs make different sounds?

1. Mixing the level of different pipes to change the harmonic content.
2. Using swell (volume) pedals to control the amount of air passing though the pipes.

That's it.

Electronic organs duplicate the swell pedal(s) and to get the effect of mixing pipes (as AG noted) Hammond organs stack up sine waves in the normal harmonic series and most other electric organs (like Farfisas and Voxes) use filtered square and saw waves (hmm, that sounds familiar).

The basic patch found in the memory of many programmable synths will be a sawtooth wave, filter wide open, amp envelope set to A, D, R all 0 and S at maximum. Sounds like a transistor organ, dunnit? Close the filter (but do not sweep it while playing) and it still sounds like an organ sound.

This is why experienced synthesists constantly rave about modulation options because without EGs, LFOs, velocity control and the like it's just an organ.

If you read up on string and "ensemble" synths you'll find they are closely related to transistor organs. The Solina was made by Eminent who were an Italian organ company.

[zmd]

The playing method is typically the same as well. guitars/violins/horns/etc have a very accidental interface, whereas keyboards are very deliberate.

You mean accidental like a saxophone reed accidentally being clamped to a mouthpiece and the randomly drilled holes that produce different tones when plugged with keys that just happen to be the same size?

surprisingly no! What I mean is that with the instruments I mentioned and many others there is an inherent lack of precision in the interface. for example on a guitar, the one I am most familiar with, when you press a string it is nearly a guarantee that you will impart some pitch bend either by pulling or pushing on the string harder than anticipated. bearing in mind that I am talking on a very subtle level here.
the organ, unless it is in terrible shape, still just gives you the one option when you press a key... A lot closer to a synthesizer.

[madtheory]

... there is an inherent lack of precision in the interface...

Or with practice and skill, totally intuitive tactile control (see: Thinking, Fast and Slow by Daniel Kahnemann).

[GuyaGuy]

The playing method is typically the same as well. guitars/violins/horns/etc have a very accidental interface, whereas keyboards are very deliberate.

You mean accidental like a saxophone reed accidentally being clamped to a mouthpiece and the randomly drilled holes that produce different tones when plugged with keys that just happen to be the same size?

surprisingly no! What I mean is that with the instruments I mentioned and many others there is an inherent lack of precision in the interface. for example on a guitar, the one I am most familiar with, when you press a string it is nearly a guarantee that you will impart some pitch bend either by pulling or pushing on the string harder than anticipated. bearing in mind that I am talking on a very subtle level here.
the organ, unless it is in terrible shape, still just gives you the one option when you press a key... A lot closer to a synthesizer.

Then accidental wasn't the word you were looking for. An accidental interface would be the tab of a banana peel making it so easy to open.

And a keyboard is less precise as an interface unless you are mostly interested in binary logic in your playing. For precise control over glissando and volume, a trombone or violin are much better equipped, for example. I think what you're trying to say is that it's limited as an interface because it's primarily a note on/off function. Of course we are only taking about synths with keys and there are plenty of other interfaces...

[mpa1104]

So how do pipe organs make different sounds?

1. Mixing the level of different pipes to change the harmonic content.

If with the word "level" you mean mixing the combination of ranks of pipes (ie, what you hear when you pull a drawstop), then yes, but you can't change the volume level of each rank of pipes. The only way to affect a volume change is ... (see next point)

2. Using swell (volume) pedals to control the amount of air passing though the pipes.

Not really true. Swell pedals on pipe organs don't control air. They control the opening and closing of shutters (or shades as they're sometimes called) on a large box. The box houses all the pipes of an enclosed division (on a 3 or 4 manual organ, 1 or 2 of the manuals may be enclosed, not all manuals of a pipe organ are enclosed unless it's a "unit" organ). The Swell pedal therefore, has the effect of both volume and a bit of filtering, depending on how well the box has been soundproofed (Some European builders built double walled boxes with sand between the walls. Some of the softer voiced ranks were almost inaudible. This gave a new means of expression which made quite a difference to the "symphonic" style of organ building - and playing - in the 19th century).

Also, don't forget "mutation" ranks - these were ranks of pipes that do not play the actual pitch triggered on the keyboard. For example, if you played a middle C using a stop of length 2-2/3, you'll hear a G sounding 2.5 octaves higher. These of course, could be used to accentuate overtones.

Anyway, steering OT here sorry (but I'm an organist so it's my favourite topic when it comes up ). Essentially the answers to why organs are easy to synthesise have already been given. That said, there is still a lot of "finessing" one can do to an otherwise basic organ sound to give it a bit of an edge.

[madtheory]

An accidental interface would be the tab of a banana peel making it so easy to open.

And while we're all correcting each other, the ease of peeling a banana is not accidental. It was domesticated/bred/ cultivated to achieve that, just like all the other fruit we eat, over thousands of years by farmers:
http://en.wikipedia.org/wiki/Banana#His ... ultivation

Anyway, back to organs

[mpa1104]

I just keep looking at 'accidental banana peel' and thinking "what a great band name"

[zmd]

Then accidental wasn't the word you were looking for. An accidental interface would be the tab of a banana peel making it so easy to open.

And a keyboard is less precise as an interface unless you are mostly interested in binary logic in your playing. For precise control over glissando and volume, a trombone or violin are much better equipped, for example. I think what you're trying to say is that it's limited as an interface because it's primarily a note on/off function. Of course we are only taking about synths with keys and there are plenty of other interfaces...

I don't find any of this terribly important for my point to the OP. So to simplify... you can play them the exact same way.