diff --git a/friture/spectrumPlotWidget.py b/friture/spectrumPlotWidget.py
index 2203bd84..837aed2b 100644
--- a/friture/spectrumPlotWidget.py
+++ b/friture/spectrumPlotWidget.py
@@ -356,37 +356,51 @@ def prepareQuadData(self, x, y, w, baseline, r, g, b):
 
         n = x.shape[0]
 
-        # 4 vertices per quad * (3 coordinates + 3 color coordinates)
-        if self.vertices_data.shape != (n*4, 6):
-            self.vertices_data = zeros((n*4, 6), dtype=np.float32)
-
-        self.vertices_data[0::4, 0::6] = x[:,np.newaxis]
-        self.vertices_data[0::4, 1::6] = (y + h)[:,np.newaxis]
-        self.vertices_data[0::4, 2::6] = 0*x[:,np.newaxis]
-        self.vertices_data[0::4, 3::6] = r[:,np.newaxis]
-        self.vertices_data[0::4, 4::6] = g[:,np.newaxis]
-        self.vertices_data[0::4, 5::6] = b[:,np.newaxis]
-
-        self.vertices_data[1::4, 0::6] = (x + w)[:,np.newaxis]
-        self.vertices_data[1::4, 1::6] = (y + h)[:,np.newaxis]
-        self.vertices_data[1::4, 2::6] = 0*x[:,np.newaxis]
-        self.vertices_data[1::4, 3::6] = r[:,np.newaxis]
-        self.vertices_data[1::4, 4::6] = g[:,np.newaxis]
-        self.vertices_data[1::4, 5::6] = b[:,np.newaxis]
-
-        self.vertices_data[2::4, 0::6] = x[:,np.newaxis]
-        self.vertices_data[2::4, 1::6] = y[:,np.newaxis]
-        self.vertices_data[2::4, 2::6] = 0*x[:,np.newaxis]
-        self.vertices_data[2::4, 3::6] = r[:,np.newaxis]
-        self.vertices_data[2::4, 4::6] = g[:,np.newaxis]
-        self.vertices_data[2::4, 5::6] = b[:,np.newaxis]
-
-        self.vertices_data[3::4, 0::6] = (x + w)[:,np.newaxis]
-        self.vertices_data[3::4, 1::6] = y[:,np.newaxis]
-        self.vertices_data[3::4, 2::6] = 0*x[:,np.newaxis]
-        self.vertices_data[3::4, 3::6] = r[:,np.newaxis]
-        self.vertices_data[3::4, 4::6] = g[:,np.newaxis]
-        self.vertices_data[3::4, 5::6] = b[:,np.newaxis]
+        # (1 quad = 2 triangles = 6 vertices) * (3 coordinates + 3 color coordinates)
+        if self.vertices_data.shape != (n*6, 6):
+            self.vertices_data = zeros((n*6, 6), dtype=np.float32)
+
+        self.vertices_data[0::6, 0::6] = x[:,np.newaxis]
+        self.vertices_data[0::6, 1::6] = (y + h)[:,np.newaxis]
+        self.vertices_data[0::6, 2::6] = 0*x[:,np.newaxis]
+        self.vertices_data[0::6, 3::6] = r[:,np.newaxis]
+        self.vertices_data[0::6, 4::6] = g[:,np.newaxis]
+        self.vertices_data[0::6, 5::6] = b[:,np.newaxis]
+
+        self.vertices_data[1::6, 0::6] = (x + w)[:,np.newaxis]
+        self.vertices_data[1::6, 1::6] = (y + h)[:,np.newaxis]
+        self.vertices_data[1::6, 2::6] = 0*x[:,np.newaxis]
+        self.vertices_data[1::6, 3::6] = r[:,np.newaxis]
+        self.vertices_data[1::6, 4::6] = g[:,np.newaxis]
+        self.vertices_data[1::6, 5::6] = b[:,np.newaxis]
+
+        self.vertices_data[2::6, 0::6] = x[:,np.newaxis]
+        self.vertices_data[2::6, 1::6] = y[:,np.newaxis]
+        self.vertices_data[2::6, 2::6] = 0*x[:,np.newaxis]
+        self.vertices_data[2::6, 3::6] = r[:,np.newaxis]
+        self.vertices_data[2::6, 4::6] = g[:,np.newaxis]
+        self.vertices_data[2::6, 5::6] = b[:,np.newaxis]
+
+        self.vertices_data[3::6, 0::6] = x[:,np.newaxis]
+        self.vertices_data[3::6, 1::6] = y[:,np.newaxis]
+        self.vertices_data[3::6, 2::6] = 0*x[:,np.newaxis]
+        self.vertices_data[3::6, 3::6] = r[:,np.newaxis]
+        self.vertices_data[3::6, 4::6] = g[:,np.newaxis]
+        self.vertices_data[3::6, 5::6] = b[:,np.newaxis]
+
+        self.vertices_data[4::6, 0::6] = (x + w)[:,np.newaxis]
+        self.vertices_data[4::6, 1::6] = y[:,np.newaxis]
+        self.vertices_data[4::6, 2::6] = 0*x[:,np.newaxis]
+        self.vertices_data[4::6, 3::6] = r[:,np.newaxis]
+        self.vertices_data[4::6, 4::6] = g[:,np.newaxis]
+        self.vertices_data[4::6, 5::6] = b[:,np.newaxis]
+
+        self.vertices_data[5::6, 0::6] = (x + w)[:,np.newaxis]
+        self.vertices_data[5::6, 1::6] = (y + h)[:,np.newaxis]
+        self.vertices_data[5::6, 2::6] = 0*x[:,np.newaxis]
+        self.vertices_data[5::6, 3::6] = r[:,np.newaxis]
+        self.vertices_data[5::6, 4::6] = g[:,np.newaxis]
+        self.vertices_data[5::6, 5::6] = b[:,np.newaxis]
 
     def transformUpdate(self):
         self.need_transform = True
@@ -459,7 +473,7 @@ def glDraw(self, xMap, yMap, rect, vbo, shader_program):
             color_offset  = c_void_p(3 * sizeof(c_float))
             GL.glVertexAttribPointer(0, 3, GL.GL_FLOAT, GL.GL_FALSE, stride, vertex_offset)
             GL.glVertexAttribPointer(1, 3, GL.GL_FLOAT, GL.GL_FALSE, stride, color_offset)
-            GL.glDrawArrays(GL.GL_TRIANGLE_STRIP, 0, self.vertices_data.shape[0])
+            GL.glDrawArrays(GL.GL_TRIANGLES, 0, self.vertices_data.shape[0])
             GL.glDisableVertexAttribArray(0)
             GL.glDisableVertexAttribArray(1)
         finally: