add moddelay cmd

doc/README.md

@@ -293,7 +293,7 @@ GVerb algorithm from SWH plugins.
 
 > A utility plugin that inverts the signal, also (wrongly) known as a 180 degree phase shift.
 
-## `tapedelay split index`
+## `tapedelay split index speed da_db t1d t1a_db...`
 
 **TODO:** gives 0 output
 
@@ -311,3 +311,9 @@ GVerb algorithm from SWH plugins.
  - t3a\_db (tap 3 level, dB): -90..0, default -90
  - t4d (tap 4 distance, inches): 0..4, default 3
  - t4a\_db (tap 4 level, dB): -90..0, default -90
+
+## `moddelay split index`
+
+> A delay whose tap can be modulated at audio rate.
+
+ - base (base delay, seconds): 0..1, default 1