diff --git a/src/samplesrc/a2pwm/readme.md b/src/samplesrc/a2pwm/readme.md
index c7b5960..412576f 100644
--- a/src/samplesrc/a2pwm/readme.md
+++ b/src/samplesrc/a2pwm/readme.md
@@ -41,7 +41,11 @@ The duration of the note is in increments of 0.0255 seconds (the PWM loop is 100
     /              SAVE ABS MACRO
     ?              SAVE REL MACRO
     P              PERSISTANT STATE
+    0              TOGGLE SPEAKER PHASE
 
 Command keys and note keys can be interspersed together.
 ### Recording Macros
 One of the most powerful features of the Oscillation Overthruster is macro recording. There are seven macros that can be assigned to the lower row of keys, Z ... M. To record one of the macros, type the key along with the CONTROL key to begin recording. The RECORDING text will show up to the right of the text panel during recording. When recording, other macros can be called, allowing nested calls. However, recursive macros cannot be made, i.e. macro Z calling macro X calling macro Z. If, during recording, you want to cancel the macro, press ESCape. Their are two ways to save the macro: absolute and relative. An absolute macro will retain the state settings at the time the macro is recorded. Octave, duration, and LFO settings are restored before the macro is played, then restored when it is done. A relative macro will use the current settings when playing back. To record a rest, the spacebar will insert a pause for the length of the current duration. You can make the current macros persistent by pressing 'P' to write the macros and current settings to disk for the next time.
+
+## A note about speaker phase
+I discovered that the Apple ][ and Apple //e are affected by the initial phase of the speaker when implementing volume control with PWM. Interestingly, the Apple //c and emulators aren't impacted by the speaker phase. The hack was to add a command to flip the speaker phase (the '0' key). If you notice diminished volume when you run Oscillation Overthruster, press '0' to see if it doesn't clear up the problem. I hope to find a solid solution to this someday, but this is the fix for now.