The Basic Organ Pipe


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Here is where we’ll begin making a basic pipe organ.  Pipe organs are basically “blown pipes”, and we’ve already done that, so we’re most of the way there.


Some differences are:


  • Organs are polyphonic.  Our earlier pipes were monophonic, and we eventually added extra logic to simulate the smooth note-to-note transitions.  That won’t be necessary here.


  • Organ pipes don’t have much expressive ability, when compared to a flute or recorder.  It’s basically a pipe, a supply of compressed air, and a switch.


  • When you press a key on an organ, multiple pipes will usually sound.  It’s similar to the multiple drawbars a Hammond organ (the Hammond drawbars were modeled after pipe organs).


  • Most pipe organs have different kinds of pipes, such as flutes, diapasons, and reeds.


Here, we’ll concentrate here on flute pipes.  We’ll begin with a standard 8’ flute pipe (tuned like the 8’ drawbar on a Hammond organ).  We’ll then begin adding more pipes for a richer sound.




Our first 8’ pipe


Below is a patch for an 8’ organ pipe.  It’s in two pictures.  The second picture is the FX area, which contains a reverb module.  What’s a pipe organ without reverb?







This patch is basically a version of our earlier “blown pipe” model, with a few changes.


  • It’s polyphonic.  It pretty much has to be.


  • Most of the expressive ability has been removed.  After all, a pipe organ rank isn’t terribly expressive.  But there’s another reason:  care has been taken to minimize the DSP usage of this patch.  We’ll soon be adding more pipes, and we want to preserve as much polyphony as we can.


  • An additional SeqCtr module has been added for fine-tuning the frequency of the loop’s lowpass filter.  This lets us shape the tone of the pipe across the keyboard.  Note:  as with all lowpass filters in the loop, changing the cutoff frequency will throw the note out of tune, and require some pitch correction using the pitch SeqCtrs.




What are the controls?


Looking at the Parameter Overview, the controls are pretty simple:


  • Coarse and fine transposition controls:  This lets us transpose and tune the patch.


  • Air level:  This is a crossfader that varies the input air level from 40 to 46 Clavia units.


  • Noise level and color:  Shapes the amount and color of the air hissing in the pipe.  We could certainly appreciate something more interesting here, like a vocal filter, but we’re trying to minimize DSP usage.


  • Air envelope:  Controls the attack and release times of the incoming air.


  • Reverb:  Gotta include this in any pipe organ patch!