From fd8032872726de0321b4939b395cfd0278afa3ee Mon Sep 17 00:00:00 2001
From: Geraint <luffgd@gmail.com>
Date: Fri, 4 Jul 2025 23:47:19 +0100
Subject: [PATCH] Fade delays on chorus depth change

---
 chorus.h | 47 +++++++++++++++++++++++++++++++----------------
 1 file changed, 31 insertions(+), 16 deletions(-)

diff --git a/chorus.h b/chorus.h
index 6dc314d..02a496e 100644
--- a/chorus.h
+++ b/chorus.h
@@ -57,7 +57,7 @@ struct ChorusSTFX : public BaseEffect {
 		
 		storage.range("detune", detune)
 			.info("detune", "detuning depth")
-			.range(1, 10, 50)
+			.range(1, 8, 50)
 			.unit(" s.t.", 0);
 	}
 
@@ -73,6 +73,7 @@ struct ChorusSTFX : public BaseEffect {
 	
 	void reset() {
 		delay.reset();
+		phase = 0;
 	}
 	
 	template<class Io, class Config, class Block>
@@ -80,13 +81,16 @@ struct ChorusSTFX : public BaseEffect {
 		Sample detuneHz = detune*0.45f/depthMs; // 0.45ms oscillation at 1Hz is about 1 semitone
 		Sample phaseStep = detuneHz/config.sampleRate;
 		
-		Sample depthSamples = depthMs*0.001*config.sampleRate;
+		bool fading = depthMs.from() != depthMs.to();
+		Sample depthSamples = depthMs.to()*0.001*config.sampleRate;
+		Sample depthSamplesFrom = depthMs.from()*0.001*config.sampleRate;
 
 		std::array<Sample, 6> multiIn, multiOut;
 		std::array<Sample, 6> delaySamples;
 		
-		Sample dry = 1 - mix*mix, wet = mix*(2 - mix)/std::sqrt(Sample(6));
-
+		auto dry = block.smooth(mix, [](double m){return 1 - m*m;});
+		auto wet = block.smooth(mix, [](double m){return m*(2 - m)/std::sqrt(Sample(6));});
+		
 		for (size_t i = 0; i < block.length; ++i) {
 			for (size_t c = 0; c < 6; ++c) {
 				size_t inputC = c%config.inputChannels;
@@ -94,21 +98,32 @@ struct ChorusSTFX : public BaseEffect {
 			}
 			delay.write(multiIn);
 			
-			Complex phaseComplex = std::polar(Sample(1), phase*Sample(2*M_PI));
-			phase += phaseStep;
-			for (size_t c = 0; c < 6; ++c) {
-				Sample osc = (phaseComplex*oscillatorOffsets[c]).real();
-				delaySamples[c] = depthSamples*Sample(0.5)*(1 + osc);
-			}
-			delay.readMulti(delaySamples, multiOut);
-
-			for (size_t c = 0; c < config.outputChannels; ++c) {
-				Sample sum = 0;
+			for (size_t oc = 0; oc < config.outputChannels; ++oc) {
+				Complex phaseComplex = std::polar(Sample(1), phase*Sample(2*M_PI) + oc*Sample(2.632));
 				for (size_t c = 0; c < 6; ++c) {
-					sum += multiOut[c];
+					Sample osc = (phaseComplex*oscillatorOffsets[c]).real();
+					delaySamples[c] = depthSamples*Sample(0.5)*(1 + osc);
 				}
-				io.output[c][i] = multiIn[c]*dry + sum*wet;
+				delay.readMulti(delaySamples, multiOut);
+
+				if (fading) {
+					// read a second set of delay times, and fade between them
+					std::array<Sample, 6> multiOutFrom;
+					for (size_t c = 0; c < 6; ++c) {
+						Sample osc = (phaseComplex*oscillatorOffsets[c]).real();
+						delaySamples[c] = depthSamplesFrom*Sample(0.5)*(1 + osc);
+					}
+					delay.readMulti(delaySamples, multiOutFrom);
+					for (size_t c = 0; c < 6; ++c) {
+						multiOut[c] = block.fade(i, multiOutFrom[c], multiOut[c]);
+					}
+				}
+
+				// Arbitrarily chosen gains, 4 positive, 2 negative
+				Sample sum = multiOut[0] - multiOut[1] + multiOut[2] + multiOut[3] - multiOut[4] + multiOut[5];
+				io.output[oc][i] = multiIn[oc]*dry.at(i) + sum*wet.at(i);
 			}
+			phase += phaseStep;
 		}
 		phase -= std::floor(phase);
 	}