Update to non-real-time preview.

Fixes and updates on top of some code clean-up from Leland.

plug-ins/highpass.ny

@@ -1,7 +1,7 @@
 ;nyquist plug-in
-;version 3
+;version 4
 ;type process
-;preview enabled
+;preview linear
 ;categories "http://lv2plug.in/ns/lv2core#HighpassPlugin"
 ;name "High Pass Filter..."
 ;action "Performing High Pass Filter..."
@@ -10,7 +10,7 @@
 
 ;; highpass.ny by Dominic Mazzoni
 ;; Modified by David R. Sky
-;; Updated by Steve Daulton June 2012
+;; Updated by Steve Daulton June 2012, 2015.
 ;; Released under terms of the GNU General Public License version 2:
 ;; http://www.gnu.org/licenses/old-licenses/gpl-2.0.html .
 
@@ -20,6 +20,7 @@
 ;;control q "Filter quality (Q) for 12 dB rolloff" real "" 0.7071 .1 20
 ;control frequency "Cutoff frequency (Hz)" real "" 1000 1 20000
 
+
 (cond 
   ((> frequency (/ *sound-srate* 2))
     (format nil 
@@ -35,4 +36,4 @@
   (T 
     (funcall 
       (nth rolloff '(hp highpass2 highpass4 highpass6 highpass8))
-      s frequency)))
+      *track* frequency)))