Remilia’s Theme on Bat Detector [HD]

Posted on 2010-09-28 at 16:37 in Music, Touhou, Videos by Robbi-985.

A heterodyne bat detector lets you hear the difference (frequency-wise) between the sounds around it, and a set frequency. So, doesn’t that mean you can make ultrasonic music and then use the detector to shift the frequencies down so that a human can hear it? It sure does! =D

That said, I didn’t actually make the music – it’s the final boss theme (“Septette for a Dead Princess”) from Touhou 06 (Embodiment of Scarlet Devil), as ripped directly from the game (in MIDI format).

[Watch in HD]

I modified BaWaMI, a MIDI software synth that I made, so that you can shift the frequency of all notes up by a linear amount. This is different to simple “pitch-shifting”, which MULTIPLIES the frequencies by a set amount. That’s why it sounds horribly out-of-tune when shifted – the frequency is made to range from something other than 0 Hz. When shifted by exactly the right amount, the detector is able to recreate the sound as ranging from 0 Hz again. Because the detector is designed to be accurate to a few KHz rather than a few dozen Hz, its internal oscillator tends to “drift” a bit, so I have to keep adjusting the tuning on my program to compensate.

This bat detector is the Ciel-electronique CDB 301 (the newest revision includes a built-in speaker).

(Yes, bat videos will come some time, but they might have to wait until next summer, as little Remi is going into hibernation now >w<)

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