Those interested in a king of gnarliness that goes beyond the one produced by fuzz pedals should check out the Discomfort Designs Riemann’s Grave, which combines three filters with a sample rate crusher and 4 toggles that modify the way the signal is handled. To quote Jamie of Harsh Tones, “it makes sounds the likes of which I’ve never heard before.”
Let’s start by taking a look at the three filters, whose Resonance is controlled by the… Resonance knob (yes, it affects all three filters):
SWP (Sweep Filter:) This is a filter controlled by the footswitch on the right. Pressing the footswitch will momentarily close it and then gradually reopen it, with the sweep’s speed set by the sweep knob.
Theorem 1: This is a resonant 24 dB per octave low pass filter. With toggle 1 pointing down, the cutoff frequency follows the knob. With toggle 1 pointing up, random modulation is applied to the cutoff frequency, and the knob controls how rapidly a new cutoff frequency is selected in the random cycle.
Theorem 2: A second resonant LPF whose cutoff frequency can be modulated either by a curvy (sine wave) or pointy (ramp wave) shaped LFO, whose speed is controlled by the rate knob. Toggle 3 will select the LFO wave shape. Toggle 4 will choose a constant (down) or random (up) modulated LFO.
Then there is the sample rate reducer section, controlled via the Zeta Function knob, which, at higher settings, will make your sample sound very lo-fi or, at extreme settings, atonal and bizarre (try that on drums!). In fixed mode (Toggle 2 down) the knob controls the amount of reduction, while in random mode (Toggle 2 pointing up) the knob controls how quickly a new rate of crushing is selected, which is a pretty unique feature.
This pedal is rather insane, have a blast!
Discomfort Designs Riemann’s Grave, Builder’s Notes
What have we got here? Riemann’s Grave is a curated trio of biquad filters paired with a sample rate reducer. So you can filter your freqs and crush your bits in some very unique, interesting, and uncomfortable ways. It’s also named for a dead mathematician.
Mix: This knob controls the wet/dry mix. By law, there has to be a mix knob. Without a mix knob, we all go to jail.
Resonance: (RES) This is a universal parameter that adds emphasis to the cutoff frequency of all three filters. High levels of resonance will get extreme results! One way to use resonance is with a fixed filter to really push a specific frequency range. Another way is to use with a modulated filter to get flubbly-whubbly sounds. There are probably other uses, but no one knows about them anymore.
Sweep Filter: (SWP) This bounceable LPF is controlled by the footswitch on the right. Pressing the foot switch will momentarily close the filter (set the cut off frequency to zero) and it will gradually return to an open position, according to the setting of the sweep knob. Turn CW for slower and longer sweeps.
Theorem 1: The first filter, a resonant 24 dB per octave low pass filter. With toggle 1 pointing down, the cutoff frequency is fixed. Turn CW to close the filter, CCW to open. With toggle 1 pointing up, random modulation is applied to the cutoff frequency. Turning CW now controls how rapidly an new cutoff frequency is selected.
Zeta Function: This controls the sample rate reduction/bit crushing. Higher settings will mangle and crush, and create some wonderfully ugly atonal messy sounds. Drums love that kind of thing. In fixed mode (Toggle 2 down) the knob controls the amount of reduction, turn CW for lower sample rates. In random mode (Toggle 2 pointing up) the knob controls how often a new rate of crushing is selected.
Theorem 2: The second filter, also a resonant LPF. The cutoff frequency of this filter is modulated either by a curvy (sine wave) or pointy (ramp wave) shaped LFO. The speed of LFO is controlled by the rate knob. Toggle 3 will select the LFO wave shape. Toggle 4 will choose a constant (down) or random (up) modulated LFO.