diff --git a/Timeline/Control_Sequence.C b/Timeline/Control_Sequence.C
index b6bbabf..273e955 100644
--- a/Timeline/Control_Sequence.C
+++ b/Timeline/Control_Sequence.C
@@ -319,7 +319,8 @@ Control_Sequence::handle ( int m )
 static inline float
 linear_interpolate ( float y1, float y2, float mu )
 {
-    return y1 + mu * ( y2 - y1 );
+//    return y1 + mu * ( y2 - y1 );
+    return y1 * ( 1.0f - mu ) + y2 * mu;
 }
 
 static inline float
@@ -328,23 +329,6 @@ sigmoid_interpolate ( float y1, float y2, float mu )
     return linear_interpolate( y1, y2, ( 1 - cos( mu * M_PI ) ) / 2 );
 }
 
-static inline float
-quadratic_interpolate ( float y1, float y2, float mu )
-{
-    return ( y1 * y1 ) * ( mu * mu ) + ( 2.0f * y1 * y2 ) * mu * ( y1 * y1 );
-}
-
-/* static inline float */
-/* quadratic_interpolate ( float y1, float y2, float mu ) */
-/* { */
-/* } */
-
-/* static inline float */
-/* exponential_interpolate ( float y1, float y2, float mu ) */
-/* { */
-/* //    return y1 * pow( y2 / y1, mu ); */
-/* } */
-
 /* THREAD: ?? */
 /** fill buf with /nframes/ of interpolated control curve values
  * starting at /frame/  */
@@ -363,22 +347,25 @@ Control_Sequence::play ( sample_t *buf, nframes_t frame, nframes_t nframes )
         if ( p2->when() < frame )
             continue;
 
-        nframes_t d = p2->when() - p1->when();
+        /* do incremental linear interpolation */
 
-        for ( nframes_t i = frame - p1->when(); i < d; ++i )
-        {
-//            *(buf++) = 1.0f - ( 2 * sigmoid_interpolate( p1->control(), p2->control(), i / (float)d ) );
-            *(buf++) = 1.0f - ( 2 * linear_interpolate( p1->control(), p2->control(), i / (float)d ) );
-//            *(buf++) = 1.0f - ( 2 * quadratic_interpolate( p1->control(), p2->control(), i / (float)d ) );
+        const nframes_t len = p2->when() - p1->when();
 
-            if ( ! n-- )
-                return nframes;
+        /* scale to -1.0 to 1.0 */
+        const float y1 = 1.0f - ( 2.0f * p1->control() );
+        const float y2 = 1.0f - ( 2.0f * p2->control() );
+
+        const nframes_t start = frame - p1->when();
+        const float incr = ( y2 - y1 ) / (float)len;
+
+        float v = y1 + start * incr;
+
+        for ( nframes_t i = start; i < len && n--; ++i, v += incr )
+            *(buf++) = v;
 
-            frame++;
-        }
     }
 
-    return frame;
+    return nframes - n;
 }
 
 
diff --git a/Timeline/Disk_Stream.C b/Timeline/Disk_Stream.C
index f30d280..df42447 100644
--- a/Timeline/Disk_Stream.C
+++ b/Timeline/Disk_Stream.C
@@ -50,7 +50,7 @@
 /* TODO: read/write data from/to disk in larger chunks to avoid
  * excessive seeking. 256k is supposedly the sweetspot. */
 
-//float Disk_Stream::seconds_to_buffer = 5.0f;
+// float Disk_Stream::seconds_to_buffer = 5.0f;
 float Disk_Stream::seconds_to_buffer = 2.0f;
 // size_t Disk_Stream::disk_block_frames = 2048;
 
diff --git a/Timeline/Playback_DS.C b/Timeline/Playback_DS.C
index d99b1b5..e53ddbd 100644
--- a/Timeline/Playback_DS.C
+++ b/Timeline/Playback_DS.C
@@ -142,12 +142,13 @@ Playback_DS::disk_thread ( void )
 
         for ( int i = channels(); i--; )
         {
-            while ( jack_ringbuffer_write_space( _rb[ i ] ) < block_size )
-            {
-                printf( "IO: disk buffer overrun!\n" );
-                /* FIXME: is this *really* the right thing to do?  */
-                usleep( 2000 );
-            }
+
+/*             while ( jack_ringbuffer_write_space( _rb[ i ] ) < block_size ) */
+/*             { */
+/*                 printf( "IO: disk buffer overrun!\n" ); */
+/*                 /\* FIXME: is this *really* the right thing to do?  *\/ */
+/*                 usleep( 2000 ); */
+/*             } */
 
             /* deinterleave direcectly into the ringbuffer to avoid
              * unnecessary copying */