diff --git a/ysynth.py b/ysynth.py
index 0cfc3e8..ca53370 100644
--- a/ysynth.py
+++ b/ysynth.py
@@ -5,6 +5,8 @@
 from pymod import _ysynth_init, _ysynth_init, _ysynth_set_callback
 from math import cos, sin, pi, modf
 from itertools import izip
+import numpy as np
+from scipy.signal import lfilter
 
 __all__ = ['YSynth', 'Sin', 'Cos', 'Saw', 'RevSaw', 'Square', 'Pulse']
 
@@ -50,13 +52,15 @@ class YSynth(object):
 
         # Process audio graph
         buf_len = len(channels[0])
-        for i in xrange(buf_len):
-            next_sample = next(self.graph)
-            for j in xrange(len(channels)):
-                channels[j][i] = next_sample
+        self.chunk_size = buf_len
 
-            # Advance sampleclock
-            self.samples += 1
+        next_chunk = next(self.graph)
+        for j in xrange(len(channels)):
+            for i in xrange(buf_len):
+                channels[j][i] = next_chunk[i]
+
+        # Advance sampleclock
+        self.samples += buf_len
 
     def set_graph(self, graph):
         graph.set_synth(self)
@@ -288,13 +292,25 @@ class YOscillator(YAudioGraphNode):
             The generated cycle ranges from 0.0 to 1.0 exclusive.
             """
 
-            cycle = 0.0
-            samples = 0
+            last_cycle = [0.0]
 
             for freq, in l:
-                cycle = freq * samples / float(self.synth.samplerate)
-                yield modf(cycle)[0]
-                samples = (samples + 1) % self.synth.samplerate
+                # The last_cycle will only be a list during the initial
+                # iteration, perfect for a 'once' statement, we want
+                # to force the first cycle value to 0.
+                if isinstance(last_cycle, list):
+                    if isinstance(freq, np.ndarray):
+                        ifreq = freq[0]
+                    else:
+                        ifreq = freq
+                    last_cycle = [-(ifreq / float(self.synth.samplerate))]
+
+                # Compute cycle using IIR filter and np.fmod
+                cycle, last_cycle = lfilter([1], [1, -1], freq /
+                    float(self.synth.samplerate) *
+                    np.ones(self.synth.chunk_size), zi=last_cycle)
+                yield np.fmod(cycle, 1.0)
+                last_cycle = np.fmod(last_cycle, 1.0)
 
         return self.oscillate(cycle_gen())
 
@@ -308,7 +324,7 @@ class Sin(YOscillator):
     """
     def oscillate(self, l):
         for pos in l:
-            yield sin(pos * 2 * pi)
+            yield np.sin(2 * pi * pos)
 
 class Cos(YOscillator):
     """
@@ -316,7 +332,7 @@ class Cos(YOscillator):
     """
     def oscillate(self, l):
         for pos in l:
-            yield cos(pos * 2 * pi)
+            yield np.cos(2 * pi * pos)
 
 class Saw(YOscillator):
     """
@@ -340,15 +356,17 @@ class Square(YOscillator):
     """
     def oscillate(self, l):
         for pos in l:
-            yield 1.0 if pos < 0.5 else -1.0
+            #yield 1.0 if pos < 0.5 else -1.0
+            pos = pos - 0.5
+            yield -(np.abs(pos) / pos)
 
 class Pulse(YOscillator):
     """
     Pulse oscillator
     """
     def oscillate(self, l):
-        prev_pos = 1.0
+        zi = [1.0]
         for pos in l:
-            yield 1.0 if pos < prev_pos else 0.0
-            prev_pos = pos
+            pos, zi = lfilter([-1, 1], [1], pos, zi=zi)
+            yield np.array(pos > 0, dtype=float)