diff --git a/libs/ardour/ardour/coreaudio_source.h b/libs/ardour/ardour/coreaudio_source.h
index c8634cb9e2..6ae74b7304 100644
--- a/libs/ardour/ardour/coreaudio_source.h
+++ b/libs/ardour/ardour/coreaudio_source.h
@@ -42,7 +42,6 @@ class CoreAudioSource : public ExternalSource {
 	mutable PBD::Lock _tmpbuf_lock;
 
 	void init (const string &str, bool build_peak);
-	jack_nframes_t read_unlocked (Sample *dst, jack_nframes_t start, jack_nframes_t cnt, char * workbuf) const;
 };
 
 }; /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/externalsource.h b/libs/ardour/ardour/externalsource.h
index 3ba19dc1d5..17504d0afc 100644
--- a/libs/ardour/ardour/externalsource.h
+++ b/libs/ardour/ardour/externalsource.h
@@ -58,8 +58,7 @@ class ExternalSource : public Source {
 	uint16_t channel;
 	string  _path;
 
-	virtual void init (const string &str, bool build_peak) = 0;
-	virtual jack_nframes_t read_unlocked (Sample *dst, jack_nframes_t start, jack_nframes_t cnt, char * workbuf) const;
+	jack_nframes_t read_unlocked (Sample *dst, jack_nframes_t start, jack_nframes_t cnt, char * workbuf) const;
 };
 
 }; /* namespace ARDOUR */
diff --git a/libs/ardour/ardour/sndfilesource.h b/libs/ardour/ardour/sndfilesource.h
index 53e5b9df67..37167e6a9a 100644
--- a/libs/ardour/ardour/sndfilesource.h
+++ b/libs/ardour/ardour/sndfilesource.h
@@ -46,7 +46,6 @@ class SndFileSource : public ExternalSource {
 	mutable PBD::Lock _tmpbuf_lock;
 
 	void init (const string &str, bool build_peak);
-	jack_nframes_t read_unlocked (Sample *dst, jack_nframes_t start, jack_nframes_t cnt, char * workbuf) const;
 };
 
 }; /* namespace ARDOUR */
diff --git a/libs/ardour/externalsource.cc b/libs/ardour/externalsource.cc
index de560bfce5..568100ca44 100644
--- a/libs/ardour/externalsource.cc
+++ b/libs/ardour/externalsource.cc
@@ -90,18 +90,63 @@ ExternalSource::old_peak_path (string audio_path)
 	return peak_path (audio_path);
 }
 
+#ifdef HAVE_COREAUDIO
+
+ExternalSource*
+ExternalSource::create (const XMLNode& node)
+{
+	ExternalSource* es = 0;
+
+	try {
+		es = new CoreAudioSource (node);
+	} 
+	
+	catch (failed_constructor& err) {
+		es = new SndFileSource (node);
+	}
+
+	es = new SndFileSource (node);
+
+	return es;
+}
+
+#else
+
 ExternalSource*
 ExternalSource::create (const XMLNode& node)
 {
 	return new SndFileSource (node);
 }
 
+#endif // HAVE_COREAUDIO
+
+#ifdef HAVE_COREAUDIO
+ExternalSource*
+ExternalSource::create (const string& idstr, bool build_peak)
+{
+	ExternalSource* es = 0;
+
+	try {
+		es = new CoreAudioSource (idstr, build_peak);
+	}
+
+	catch (failed_constructor& err) {
+		es = new SndFileSource (idstr, build_peak);
+	}
+
+	return es;
+}
+
+#else
+
 ExternalSource*
 ExternalSource::create (const string& idstr, bool build_peak)
 {
 	return new SndFileSource (idstr, build_peak);
 }
 
+#endif // HAVE_COREAUDIO
+
 #ifdef HAVE_COREAUDIO
 std::string 
 CFStringRefToStdString(CFStringRef stringRef)