Software Vocoding with the Stylophone
So as I said a few weeks ago, I have a Stylophone which is essentially a pocket synthesizer. What I got the idea to to is use the Stylophone as my synth device in post-processing vocoding. I needed to do it post because I don’t (think I) have any equipment that would make me able to vocode audio on the fly. Oh yeah, almost forgot, a vocoder is a device that takes sound (usually a modulated sound like a voice), reduces the amount of information used to store it, and then turns it back into sound by oscillating it according to frequencies in a carrier sound. Basically, you can make mechanical/robotic voices using it.
![](/images/uploads/2008/11/stypho_lg.jpg)
So I wanted to make a robot voice using… oh… say… some podcast audio. So first, I trimmed out a little bit of podcast audio in Audacity, my favorite open-source audio editor, which was easy enough. Second, I rigged my Stylophone to my computers audio input and recorded a tone in audacity with vibrato turned on. I wasn’t sure what would be best, so I tried vibrato on, vibrato off, I changed notes while playing, adjusted pitch, etc. I wanted variety. So after I got the tones I wanted, I chopped out the empty space, the mess ups, etc to have a nice flowing audio sample.
So now I had the original audio and my Stylophone audio. How do I vocode? I found a wonderful program a while back called Zerius Vocoder. Now you have to note, its pretty basic and has only a few features, but gets the job done. Also, its free, which is always nice when you’re looking for software to try out.
![](/images/uploads/2008/11/vocoder.png)
The Modulator file is my podcast sample, the Carrier file is my Stylophone file, and the Output file is the output. As for the options, I messed around with those until I found what I perceived to be the best combination. There’s always the “Restore Defaults” button if you mess up and want to redo the options.
So after hitting “Vocode”, I have my finished file all ready and waiting to be played. Here are the files I used below…
After I finished making my new file, I decided to see just exactly how the frequencies changed using another great free tool, Spectro which gives spectrograms of audio waves. So using this, I was able to have visual representations of the frequencies of the audio files. See for yourself:
![This modulator file has an average frequency of 19.5KHz.](/images/uploads/2008/11/cycle.bmp)
This modulator file has an average frequency of 19.5KHz.
![This carrier file has an average frequency of 22.1KHz.](/images/uploads/2008/11/stylo.bmp)
This carrier file has an average frequency of 22.1KHz.
![This output file has an average frequency of 22.1KHz.](/images/uploads/2008/11/test.bmp)
This output file has an average frequency of 22.1KHz.
Happy vocoding!