Canon MARK IV User Manual (en)

You can append a voice memo to a captured image. The voice memo will 
be saved as a WAV sound file having the same file number as the image. 
The sound can be played back with the camera or provided software.
Select the image to which you 
want to append a voice memo.
Press the <x> button to playback images, 
then turn the <5> dial to select the image.
Record a voice memo.
While the image is displayed, press 
the <H> button for approx. 2 sec.
When [Recording memo...] appears, 
keep pressing the button and speak 
into the microphone. The maximum 
recording time for a voice memo is 30 
To end the voice memo, let go of the 
The <
> icon will be displayed on 
the top of the screen.
 Recording and Playing Voice Memos
Recording a Voice Memo
Voice memo microphone
You cannot append a voice memo to a protected image.
You cannot append a voice memo to a movie.
To record a voice memo longer than 30 sec., repeat step 2.
You can also record a voice memo once, right after image capture during 
the image review by following step 2.
A voice memo cannot be recorded with an external microphone.