diff --git a/Source/MIKMIDINoteEvent.h b/Source/MIKMIDINoteEvent.h
index 000c785b..0af94bc8 100644
--- a/Source/MIKMIDINoteEvent.h
+++ b/Source/MIKMIDINoteEvent.h
@@ -122,9 +122,9 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface MIKMIDICommand (MIKMIDINoteEventToCommands)
 
-+ (MIKArrayOf(MIKMIDICommand *) *)commandsFromNoteEvent:(MIKMIDINoteEvent *)noteEvent clock:(MIKMIDIClock *)clock;
-+ (MIKMIDINoteOnCommand *)noteOnCommandFromNoteEvent:(MIKMIDINoteEvent *)noteEvent clock:(MIKMIDIClock *)clock;
-+ (MIKMIDINoteOffCommand *)noteOffCommandFromNoteEvent:(MIKMIDINoteEvent *)noteEvent clock:(MIKMIDIClock *)clock;
++ (MIKArrayOf(MIKMIDICommand *) *)commandsFromNoteEvent:(MIKMIDINoteEvent *)noteEvent clock:(nullable MIKMIDIClock *)clock;
++ (MIKMIDINoteOnCommand *)noteOnCommandFromNoteEvent:(MIKMIDINoteEvent *)noteEvent clock:(nullable MIKMIDIClock *)clock;
++ (MIKMIDINoteOffCommand *)noteOffCommandFromNoteEvent:(MIKMIDINoteEvent *)noteEvent clock:(nullable MIKMIDIClock *)clock;
 
 @end
 
diff --git a/Source/MIKMIDISynthesizerInstrument.h b/Source/MIKMIDISynthesizerInstrument.h
index 2b19e158..97fb1c53 100644
--- a/Source/MIKMIDISynthesizerInstrument.h
+++ b/Source/MIKMIDISynthesizerInstrument.h
@@ -25,7 +25,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  *  @return A MIKMIDISynthesizerInstrument instance with the matching instrument ID, or nil if no instrument was found.
  */
-+ (nullable instancetype)instrumentWithID:(MusicDeviceInstrumentID)instrumentID name:(NSString *)name;
++ (nullable instancetype)instrumentWithID:(MusicDeviceInstrumentID)instrumentID name:(nullable NSString *)name;
 
 /**
  *  The human readable name of the receiver. e.g. "Piano 1".
diff --git a/Source/MIKMIDITrack.h b/Source/MIKMIDITrack.h
index 592add22..19a8b5b1 100644
--- a/Source/MIKMIDITrack.h
+++ b/Source/MIKMIDITrack.h
@@ -80,7 +80,7 @@ NS_ASSUME_NONNULL_BEGIN
  *
  *  @return An array of specified class of MIDI events.
  */
-- (MIKArrayOf(MIKMIDIEvent *) *)eventsOfClass:(Class)eventClass fromTimeStamp:(MusicTimeStamp)startTimeStamp toTimeStamp:(MusicTimeStamp)endTimeStamp;
+- (MIKArrayOfKindOf(MIKMIDIEvent *) *)eventsOfClass:(Class)eventClass fromTimeStamp:(MusicTimeStamp)startTimeStamp toTimeStamp:(MusicTimeStamp)endTimeStamp;
 
 /**
  *  Gets all of the MIDI notes in the track starting from startTimeStamp and ending at endTimeStamp inclusively.