The hearing range of humans is 20Hz to 20,000Hz (20kHz). So that's our lower/upper bounds for processing data.
If we want to start with five breakpoints, this should get us started:
- 20 to 140: Bass range
- 140 to 400: Mid-Bass range
- 400 to 2600: Midrange
- 2600 to 5200: Upper Midrange
- 5200 to 20000: High end
Aha, we can probably do better, as per https://www.teachmeaudio.com/mixing/techniques/audio-spectrum/
- Sub Bass: 20 to 60 Hz
- Bass: 60 to 250 Hz
- Low Midrange: 250 to 500 Hz
- Midrange: 500 Hz to 2 kHz
- Upper Midrange: 2 to 4 kHz
- Presence: 4 kHz to 6 kHz
- Brilliance: 6 kHz to 20 kHz
For the five-bar spectrum, could just use Bass, LowMid, Mid, UpperMid, and Presence. Maybe use Sub Bass for a lighting effect?
What have we learned?
Mainly that trying to isolate frequencies is a bit like trying to pull out one bit of the cosmos for investigation: We find it tied to everything else in the cosmos. In this case, harmonics means clutter in every part of the spectrum from everything else in the spectrum. Other than the bass frequences, this entire concept isn't useful to us for visualization. We'll need to do other stuff manually, unfortunately.
Low Pass Filter - Anything LOWER than the cutoff frequency is kept. High Pass Filter - Anything HIGHER than the cutoff freq is kept.
Let's grab some key frequencies from the opening of Yuki Kajiura's "Red Rose" and see if we can make something useful out of them in Blender.
- G6 at 1500-1600 Hz (seems to be the snare, not one of the xylophone notes)
- C7 at 2000-2100 Hz
- D7 at 2300-2400 Hz
- D#7 at 2450-2530 Hz
- F7 at 2750-2850 Hz
- A#7 at 3750-3850 Hz
- C8 at 4200-4300 Hz
Actually NONE of those seem to be the xylophone notes. Let's pick something else.
- C#9 at 9000-9100 Hz
- F#9 at 12100-12200 Hz
High/low pass filtering in Audacity is helping pin things down and... yeah, it's in the 2k/4.3k range. Somehow we need to isolate each note or something. A problem for another day.
What if we go low? 550-600 Hz is the biggest peak in one slice of the Red Rose intro section.