Shimmering Choir
The sound is made up of two parts, the choir sound and the "shimmer" sound. You use a controller to crossfade between the two. This allows you to control the shimmer effect.
First the "ahhh" choir sound. It's not too hard, if you know where to start, to generate a nice vocal waveform using additive synthesis for a certain range over the keyboard, say an octave. The challenge is that if you want avoid the "chipmunk" effect as you play up the keyboard, you're probably going to want to create several waveforms, each with its own harmonic profile, one for each octave (though that's kinda of pushing it) in a four octave range starting around 98Hz.
For my K5 choir, I settled for three waveforms. Below I've listed the harmonic (linear) values for the 392Hz note:
- 1
- 1
- 0.6
- 0.02
- 0.02
- 0.03
- 0.06
- 0.1
- 0.06
- 0.02
- 0.009
- 0.01
- 0.02
- 0.02
- 0.02
- 0.02
- 0.01
This isn't based on a resynthesized choir or anything like that, just a bit of trial and error. The trick is to set up a patch as though you've already created the choir waveform, i.e. adjusted the vibrato, pitch envelope, amplitude envelope, etc. That way as you add harmonics, you can play the results to see if what you're doing is getting you closer to your goal. For an "ahhh" sound, the best place to start is to set the amplitude values for the first, second, and maybe third partials all the way to the max. Adjust these to sound right according to the range you working with (since you're only working with three or four partials, it isn't too daunting). Then add a few small peaks in the upper harmonics, say starting about an octave or two above the fundamental; you'll have to experiement a bit. These represent the vocal formats. But don't get caught up in the details. We're just going for a nice approximation. If it sounds good, it is good.
If you're not using additive synthesis, you can get a nice, warm choir pad sound by using sawtooths heavily filtered with a lowpass filter and with the resonance turned up a bit. The resonance is the key for getting it right.
Other aspects of the choir sound that are important:
Often vocalists will start flat and rise up to pitch. You can simulate this with a pitch envelope. It's a subtle but important effect. It takes some experimentation, but after a few adjustments, you'll know when you've got it right.
Next, bring in some vibrato. Delay it a bit after the attack of the sound. How much vibrato you use is determined by the sound you're going for. If you want a solo operatic sound, dial it up. If not, keep it subtle.
The attack envelope should start with a somewhat slow attack, a sorta long decay time, and a sustain level at say 75%. The release should be somewhat long, but not too long, to give the choir a chance to fade out at key release.
To create an ensemble effect, take your solo voice sound created above, and layer it with a detuned version of itself. Change the copy's rate of the vibrato and adjust the pitch envelope slightly so that the two sounds are not identicial. This enhances the ensemble effect.
Ok, unless I've forgotten something, that should give you a decent choir sound.
The "shimmer" sound is easier. You're taking a synth drawbar organ and sound and turning down the amplitude of the first two partials. You want to create an ensemble effect for this sound as you did with the choir, so create two versions of the sound detuned with respect to each other and give it a slightly different vibrato rate.
You may find that other waveforms work well to create the shimmer effect. Be sure to experiment, as always, and let me know how it turns out.
The harmonic profile of the shimmer sound:
- 0.15
- 0.4
- 1
- 1
- 1
- 1
- 1
- 1
- 1
If you're not using additive synthesis, take an organ sound and run it through a highpass filter. Adjust the filter so that it attenuates the lower harmonics.
Take the two sounds and set up a controller, maybe the pedal controller or the modulation wheel, so that as you increase the controller's value, the volume of the choir sound decreases and the volume of the shimmer sound increases. This lets you fade in the shimmer effect in real time.
Oh yeah, and be sure to drench in plenty reverb and chorus. :-)