diff --git a/smnp/module/synth/function/synth.py b/smnp/module/synth/function/synth.py
index 482faf7..913cbeb 100644
--- a/smnp/module/synth/function/synth.py
+++ b/smnp/module/synth/function/synth.py
@@ -10,6 +10,7 @@ from smnp.type.signature.matcher.type import ofTypes, ofType
 
 DEFAULT_BPM = 120
 DEFAULT_OVERTONES = [0.4, 0.3, 0.1, 0.1, 0.1]
+DEFAULT_DECAY = 4
 
 
 def getBpm(config):
@@ -46,16 +47,38 @@ def getOvertones(config):
     return DEFAULT_OVERTONES
 
 
+def getDecay(config):
+    key = Type.string("decay")
+    if key in config.value:
+        decay = config.value[key]
+        if not decay.type in [Type.INTEGER, Type.FLOAT] or decay.value < 0:
+            raise RuntimeException("The 'decay' property must be non-negative integer or float", None)
+
+        return decay.value
+
+    return DEFAULT_DECAY
+
+
+class Config:
+    def __init__(self, bpm, overtones, decay):
+        self.bpm = bpm
+        self.overtones = overtones
+        self.decay = decay
+
+    @staticmethod
+    def default():
+        return Config(DEFAULT_BPM, DEFAULT_OVERTONES, DEFAULT_DECAY)
+
 
 _signature1 = varargSignature(listOf(Type.NOTE, Type.INTEGER))
 def _function1(env, notes):
     rawNotes = [note.value for note in notes]
-    play(rawNotes, DEFAULT_BPM, DEFAULT_OVERTONES)
+    play(rawNotes, Config.default())
 
 
 _signature2 = varargSignature(ofTypes(Type.NOTE, Type.INTEGER))
 def _function2(env, notes):
-    play([ notes ], DEFAULT_BPM, DEFAULT_OVERTONES)
+    play([ notes ], Config.default())
 
 
 _signature3 = varargSignature(listOf(Type.NOTE, Type.INTEGER), ofType(Type.MAP))
@@ -63,15 +86,18 @@ def _function3(env, config, notes):
     rawNotes = [note.value for note in notes]
     bpm = getBpm(config)
     overtones = getOvertones(config)
+    decay = getDecay(config)
 
-    play(rawNotes, bpm, overtones)
+    play(rawNotes, Config(bpm, overtones, decay))
 
 
 _signature4 = varargSignature(ofTypes(Type.NOTE, Type.INTEGER), ofType(Type.MAP))
 def _function4(env, config, notes):
     bpm = getBpm(config)
     overtones = getOvertones(config)
-    play([ notes ], bpm, overtones)
+    decay = getDecay(config)
+
+    play([ notes ], Config(bpm, overtones, decay))
 
 
 function = CombinedFunction(
diff --git a/smnp/module/synth/lib/wave.py b/smnp/module/synth/lib/wave.py
index 5df57be..5c39985 100644
--- a/smnp/module/synth/lib/wave.py
+++ b/smnp/module/synth/lib/wave.py
@@ -12,14 +12,14 @@ def pause(value, bpm):
     time.sleep(60 * 4 / value / bpm)
 
 
-def play(notes, bpm, overtones):
-    compiled = compilePolyphony(notes, bpm, overtones)
+def play(notes, config):
+    compiled = compilePolyphony(notes, config)
     sd.play(compiled)
     time.sleep(len(compiled) / FS)
 
 
-def compilePolyphony(notes, bpm, overtones):
-    compiledLines = [1 / len(notes) * compileNotes(line, bpm, overtones) for line in notes]
+def compilePolyphony(notes, config):
+    compiledLines = [1 / len(notes) * compileNotes(line, config) for line in notes]
     return sum(adjustSize(compiledLines))
 
 
@@ -29,30 +29,36 @@ def adjustSize(compiledLines):
     return [np.concatenate([line, np.zeros(maxSize - len(line))]) for line in compiledLines]
 
 
-def compileNotes(notes, bpm, overtones):
+def compileNotes(notes, config):
     dispatcher = {
-        Type.NOTE: lambda note, overtones: sineForNote(note.value, bpm, overtones),
-        Type.INTEGER: lambda note, overtones: silenceForPause(note.value, bpm)
+        Type.NOTE: lambda note, overtones: sineForNote(note.value, config),
+        Type.INTEGER: lambda note, overtones: silenceForPause(note.value, config)
     }
 
-    return np.concatenate([dispatcher[note.type](note, overtones) for note in notes])
+    return np.concatenate([dispatcher[note.type](note, config) for note in notes])
 
 
-def sineForNote(note, bpm, overtones):
+def sineForNote(note, config):
     frequency = note.toFrequency()
-    duration = 60 * 4 / note.duration / bpm
+    duration = 60 * 4 / note.duration / config.bpm
     duration *= 1.5 if note.dot else 1
-    return sound(frequency, duration, overtones)
+    return sound(frequency, duration, config)
 
 
-def sound(frequency, duration, overtones):
-    return sum(a * sine((i+1) * frequency, duration) for i, a in enumerate(overtones))
+def sound(frequency, duration, config):
+    return decay(sum(a * sine((i+1) * frequency, duration) for i, a in enumerate(config.overtones)), config)
+
+
+def decay(wave, config):
+    magnitude = np.exp(-config.decay/len(wave) * np.arange(len(wave)))
+
+    return magnitude * wave
 
 
 def sine(frequency, duration):
     return (np.sin(2 * np.pi * np.arange(FS * duration) * frequency / FS)).astype(np.float32)
 
 
-def silenceForPause(value, bpm):
-    duration = 60 * 4 / value / bpm
+def silenceForPause(value, config):
+    duration = 60 * 4 / value / config.bpm
     return np.zeros(int(FS * duration))