Session 16: Mod Slots -- Flexible Routing

Objective: Use the Evolver's 4 general-purpose modulation slots to create creative modulation routings, including audio-rate modulation from oscillators and noise.

Warm-Up (2 min)

Load your vibrato + filter LFO patch from Session 15. Play a note and hear the LFO-driven movement. LFOs have dedicated destinations, but they are limited to one destination each. Mod slots give you 4 more flexible routings with a wider range of sources. Load the basic patch.

Setup

From the basic patch:

• Set Osc 3 Level to 0 and Osc 4 Level to 0
• Set LPF Frequency to 80, Resonance to 30, 4-Pole ON

Exercises

Exercise 1: Basic Mod Slot Routing (5 min)

Each mod slot has three parameters: Source, Amount, and Destination. Any source can go to any destination.

1. Press Mod 1 switch to select Mod Slot 1
2. Set Source to LF1 (LFO 1) -- this is the same as using LFO 1's own destination, but now LFO 1 can also go somewhere else simultaneously
3. Set Amount to 40
4. Set Destination to FiL (Filter Frequency)
5. Set LFO 1: Shape = Tri, Frequency = 35, Amount = 50, Destination = O1F (Osc 1 Freq -- vibrato)

Play a note. You should hear both vibrato (from LFO 1's own destination) AND filter movement (from Mod Slot 1 using LFO 1 as a source). One LFO, two destinations.

See Anu Kirk p.72 ("Modulation Slots 1-4")

Exercise 2: Audio-Rate Modulation (5 min)

Mod slots can use oscillators and noise as sources -- these are audio-rate signals that produce gritty, buzzy, or crackling effects:

1. Set Mod Slot 1: Source = Noi (Noise), Amount = 25, Destination = FiL (Filter Frequency)
2. Play a note -- you should hear a crackling, textured quality added to the filter. The noise is modulating the filter cutoff thousands of times per second
3. Increase Amount to 50 -- you should hear more aggressive, gritty modulation
4. Change Source to O3 (Digital Oscillator 3) -- you should hear a different character: a pitched, buzzy modulation at Osc 3's frequency
5. Try Source = O1 (Analog Oscillator 1) -- you should hear yet another character, with the analog oscillator's waveform imprinting on the filter

"General-purpose mod slot Sources are not filtered, so a MIDI controller going through this route will react quicker, but may produce stepping noise" -- DSI Manual p.23

Note: Mod slot sources are unfiltered (raw, fast response) unlike the dedicated MIDI controller routings which are smoothed (Anu Kirk p.72).

Exercise 3: Envelope as Mod Source (5 min)

Use ENV 3 as a mod source for more complex behavior:

1. Set Mod Slot 1: Source = En3 (Envelope 3), Amount = 60, Destination = RES (Resonance)
2. Set ENV 3: Attack = 0, Decay = 50, Sustain = 0, Release = 0, Amount = 99, Destination = OFF
3. Set LPF Frequency to 70, Resonance to 20
4. Play a note -- you should hear the resonance spike on the attack and then decay, adding a "quack" or "pop" to each note without permanently changing the base resonance
5. Now set Mod Slot 2: Source = Seq1 (Sequencer Track 1), Amount = 40, Destination = FiL
6. Program Seq 1 with varied step values (e.g., steps 1-8: 10, 80, 30, 60, 50, 20, 90, 40)
7. Press START/STOP and play -- you should hear the filter cutoff change on each sequencer step, creating a rhythmic timbral pattern while the envelope adds resonance pops

Exercise 4: Two Creative Mod Routing Patches (3 min)

Patch A -- Noise-Animated Filter:

1. Set Mod Slot 1: Source = Noi, Amount = 20, Destination = FiL
2. Set LPF Frequency to 50, Resonance to 60, 4-Pole ON
3. Set ENV 1: Attack = 0, Decay = 40, Sustain = 15, Env Amount = 80

4. Play -- you should hear punchy, gritty notes with crackling filter texture

Save as your "Noise Filter" patch.

Patch B -- Oscillator Cross-Modulation: 5. Set Mod Slot 1: Source = O3, Amount = 15, Destination = O1F (Osc 1 Frequency) 6. Set Osc 3 Level to 0 (use it only as a modulation source, not audible) 7. Set Osc 3 Shape to 1 (sine), Frequency = C2 8. Play -- you should hear Osc 1's pitch being modulated by a sine wave at Osc 3's frequency, creating FM-like effects through the mod slot

Save as your "Cross-Mod" patch.

Exploration (optional, hyperfocus days)

• Try bipolar mod amounts: Amount = -40 inverts the modulation. Set Mod Slot 1: Source = LF1, Amount = -60, Dest = FiL. The LFO now pushes the filter in the opposite direction
• Use MIDI Note Number (Nno) as a source to make any parameter track the keyboard -- great for making filter, delay, or LFO rate respond to pitch
• Set up 4 mod slots all from different sources to the same destination (e.g., all to FiL). The modulations add together, creating complex compound movement

Output Checklist

• Two creative mod routing patches saved
• Understand how to set up Source -> Amount -> Destination routing
• Heard audio-rate modulation from noise and oscillators
• Session logged in Obsidian daily note

Key Takeaways

• Mod slots let any source (LFOs, envelopes, sequencer, noise, oscillators, MIDI note, controllers) modulate any destination -- 4 flexible routing points
• Audio-rate sources (noise, oscillators) produce gritty, textured effects that cannot be achieved with LFOs alone
• Mod slot sources are unfiltered (fast but may step); dedicated MIDI controller routings are smoothed

Next Session Preview

Next time you will map velocity, aftertouch, and mod wheel to create expressive performance patches that respond to how you play -- harder, softer, with pressure and wheel gestures.