add simple envelope to stop popping

src/synth/Instrument.cpp

@@ -10,11 +10,10 @@ Instrument::Instrument(ConfigService* config, LoggerService* logger) :
 
 void Instrument::noteOn(float frequency, float velocity) {
 
-    // std::string msg = "NoteOn Frequency = " + std::to_string(frequency);
-    // if(logger_ != nullptr) logger_->log("Instrument", LogFlag::Debug, msg);
-
     phaseIncrement_ = 2.0f * pi * frequency / sampleRate_;
 
+    envelope_ += 0.01f; // so it triggers as active
+
     active_ = true;
 }
 
@@ -23,14 +22,18 @@ void Instrument::noteOff() {
 }
 
 bool Instrument::isActive() {
-    return active_;
+    return (envelope_ > 0.0f);
 }
 
 float Instrument::process(bool& scopeTrigger) {
 
+    if(active_ && envelope_ < 1.0f) envelope_ += 0.01f;
+    if(!active_ && envelope_ > 0.0f) envelope_ -= 0.01f;
+
     phase_ += phaseIncrement_;
     if(phase_ > 2.0f * pi) phase_ -= 2.0f * pi;
 
-    return sin(phase_);
+    if(!isActive()) return 0.0f;
+    return sin(phase_) * envelope_;
 
 }