Improved a couple of comments.

modules/juce_audio_processors/processors/juce_AudioPlayHead.h

@@ -130,8 +130,10 @@ public:
     /** Fills-in the given structure with details about the transport's
         position at the start of the current processing block.
 
-        This method must ONLY be called from within your AudioProcessor::processBlock()
-        method. Calling it at any other time will probably cause a nasty crash.
+        You can ONLY call this from your processBlock() method! Calling it at other
+        times will produce undefined behaviour, as the host may not have any context
+        in which a time would make sense, and some hosts will almost certainly have
+        multithreading issues if it's not called on the audio thread.
     */
     virtual bool getCurrentPosition (CurrentPositionInfo& result) = 0;
 };

modules/juce_audio_processors/processors/juce_AudioProcessor.h

@@ -140,11 +140,17 @@ public:
     /** Returns the current AudioPlayHead object that should be used to find
         out the state and position of the playhead.
 
-        You can call this from your processBlock() method, and use the AudioPlayHead
-        object to get the details about the time of the start of the block currently
-        being processed.
+        You can ONLY call this from your processBlock() method! Calling it at other
+        times will produce undefined behaviour, as the host may not have any context
+        in which a time would make sense, and some hosts will almost certainly have
+        multithreading issues if it's not called on the audio thread.
 
-        If the host hasn't supplied a playhead object, this will return nullptr.
+        The AudioPlayHead object that is returned can be used to get the details about
+        the time of the start of the block currently being processed. But do not
+        store this pointer or use it outside of the current audio callback, because
+        the host may delete or re-use it.
+
+        If the host can't or won't provide any time info, this will return nullptr.
     */
     AudioPlayHead* getPlayHead() const noexcept                 { return playHead; }