I am producing sounds for an old time vampire game. I have recorded human vocals in Latin that I would like to combine with a bat scream. It's (obviously) for a section in the game where the vampire turns into the bat.

It would be incredible if I could find a technique or a plug-in that could help manipulate the two audio regions together to make a desired "morphing" effect. I've tried a few techniques, but they have not produced the sound I was hoping for.

Please feel free to add any type of technique or idea. Would love to learn more about this type of design.


8 Answers 8


The "morph" you're describing is known as (both) spectral cross-modulation, and spectral convolution.

From what i've read in your question, I gather you're interested in essentially crossfading the two sounds together, but in the frequency domain not the time domain?

If that's indeed the case then there are a few ways to go about doing this. you can either create a patch in max 6/7 using the pfft~ object, which can get a little tricky, seeing as you'll need to learn about the Fourier Transform. You don't need to necessarily know the hard math behind it, but understand what it does, and how to properly utilize windowing and bins in the context of MSP to get the sound you're after. then it's just a matter of loading the two samples together and using a UI object (like a slider) to morph them together.

That's the simple version. If you've got a few grand to spend, get a Pacarana from Symbolic sounds - and you'll have access to what they refer to as "Tau Morphing". Essentially the same thing - but it's in real-time, and incredibly high-detail.

That's what happens when you spend 3k+ on a box with like 16 multicore CPUs in it dedicated to audio though.

Spectral convolution would work if you played with it enough, but the reality is you're looking at a lot of resampling, using a convolution reverb on the source sound - with the other sound loaded into a good convolution reverb program.

I'll tell you now. don't bother. it's a total crapshoot.

If you're unfamiliar with DSP, and you don't have the cash laying around for a Kyma Pacarana, then chances are you'll have to do this by hand, with a LOT of resampling.

The last option, which just sprang to mind, is Kontakt. It has a processing filter in it called an "AET Morph". (Authentic Expression Technology... lol fancy phrase for short term Fourier transform). you can use an AET filter, analyze a source sound, and apply the phase characteristics to another sound. Other than KSP scripting your own instruments from scratch, this is as close to Voodoo and black magic you can get in Kontakt - it would take a good few pages to walk you through the process, and most people just don't understand what their doing. Not because they're idiots or anything - it's just not very straightforward unless you understand the basic concepts behind it (Fourier Transform).

I can't afford a Pacarana, so until then, I process my cross-modulations offline in max.

do it by hand. pitch shifting, audio editing, formant shifting, etc. these are the kind of things that just take a good day of getting your hands dirty (after spending a good week reading about the process and not getting it day after day, and feeling like a moron!).

best of luck - Aaron


Maybe it's the phrasing or the cadence of speech? Sometimes that's what makes the transition sound wrong. Both "voices" should be performed similarly to seamlessly morph into the other.


Two guesses at methods - I've never actually tried either of these myself...

  1. Using an envelope follower to raise the volume of the scream dynamically with the speech.
  2. Using VocAlign to try matching the scream to the speech, ADR-style.

For both, then perhaps just cross-fading one into the other, if that's the desired final effect.


Rebal Instinct, I wonder if Dehumaniser would be of use to you? It's an app specifically designed to morph human into monster sounds and back again: http://dehumaniser.com/

That being said, I'd love to see more modern and accessible morph plugins. Aside from Prosonic/Zynaptiq Morph (which is ancient and hasn't had a major update in years) and Symbolc Sound Kyma (too costly for most and not trivial to integrate into a DAW workflow), it seems the market is really missing some cool tools to address these frequent needs — so many video games and films use creatures...


I think editing and maybe some pitch/formant shifting could get you pretty far. Sometimes convolution can work to get the tone changing to more of a Bat from human. Izotope IRIS would seem like a good tool to try also, I've never used it but it seems like this is exactly what it's supposed to help you with. I would err on the side of natural since you said it was an old time game.


Sorry to say there is no magic plugin that will achieve this effect for you. The majority of great creature vocals are painstakingly crafted by sound designers for days or even weeks.

One insight I can offer is that layering sounds is your friend. From human to bat (or vice versa) you need to weave textures from each character in and out over time, paying close attention to how these sound change and interact with each other. Sometimes a human scream can morph through some otherworldly shriek on its way to becoming a bat whistle. Or the sound of a bat chittering can shudder through some gutteral layer on its way to becoming a human laugh. It's all in the experimentation and application.


You could use a time-stretching function (such as what's built in to REAPER, Logic, or ProTools) to line up the transients of the two audio samples, and then play around with mixing and use a vocoder to apply the spectrum from one to another.


Sonic Visualiser : http://www.sonicvisualiser.org/ Would be a great place to start. It will require some work to understand the program but should be worth the effort. Also, SoundHack: http://www.soundhack.com/freeware/ may be perfect for what you need.

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