diff --git a/scripts/string_model.py b/scripts/string_model.py
new file mode 100644
index 0000000..38a0f90
--- /dev/null
+++ b/scripts/string_model.py
@@ -0,0 +1,35 @@
+
+import scipy.signal as sig
+import matplotlib.pyplot as plt
+import numpy as np
+
+# simple first order step response simulation
+# www.halvorsen.blog/documents/programming/python/resources/powerpoints/State Space Models with Python.pdf
+
+# simulation Parameters
+x0 = [0, 0]
+start = 0
+stop = 30
+step = 1
+
+t = np.arange(start,stop,step)
+K = 3
+T = 4
+
+# state-space Model
+A = [[-1/T, 0], [0, 0]]
+B = [[K/T], [0]]
+C = [[1, 0]]
+D = 0
+sys = sig.StateSpace(A, B, C, D)
+
+# step Response
+t, y = sig.step(sys, x0, t)
+
+# plotting
+plt.plot(t, y)
+plt.title("Step Response")
+plt.xlabel("t")
+plt.ylabel("y")
+plt.grid()
+plt.show()
diff --git a/src/synth/Instrument.cpp b/src/synth/Instrument.cpp
index 6f46d52..b0700b6 100644
--- a/src/synth/Instrument.cpp
+++ b/src/synth/Instrument.cpp
@@ -28,7 +28,7 @@ bool Instrument::isActive() {
 float Instrument::process(bool& scopeTrigger) {
 
     if(active_ && envelope_ < 1.0f) envelope_ += 0.01f;
-    if(!active_ && envelope_ > 0.0f) envelope_ -= 0.01f;
+    if(!active_ && envelope_ > 0.0f) envelope_ -= 0.0004f;
 
     phase_ += phaseIncrement_;
     if(phase_ > 2.0f * pi) {
@@ -37,6 +37,10 @@ float Instrument::process(bool& scopeTrigger) {
     }
 
     if(!isActive()) return 0.0f;
-    return sin(phase_) * envelope_;
+
+    // float sample = sin(phase_);
+    float sample = phase_ / pi - 1.0f; // saw
+
+    return sample * envelope_;
 
 }
diff --git a/src/synth/Synth.cpp b/src/synth/Synth.cpp
index b16d9c2..5707c77 100644
--- a/src/synth/Synth.cpp
+++ b/src/synth/Synth.cpp
@@ -10,12 +10,19 @@ Synth::Synth(ConfigService* config, LoggerService* logger, ScopeBuffer* scope, N
 
 void Synth::handleNoteEvent(const NoteEvent& event) {
 
-    Voice* v = findVoiceByNote(event.note);
-    if(v != nullptr) v->noteOff();
+    // Voice* v = findVoiceByNote(event.note);
+    // if(v != nullptr) v->noteOff();
+
+    // stop all voices that are currently playing this note
+    for(Voice& v : voices_) {
+        if(v.isActive() && v.note() == event.note) {
+            v.noteOff();
+        }
+    }
 
     if(event.type == NoteEventType::NoteOn) {
 
-        v = findFreeVoice();
+        Voice* v = findFreeVoice();
         if(v != nullptr) v->noteOn(event.note, event.velocity);
     }