Lecture-recording apps

[aagaag]

I often find myself wishing to record the audio of a lecture (but not the video) while shooting occasional pics of the slides that are shown. Is here any software that would allow me to so that in a synchronized manner, so that I can play back the auto and show the cared slides al the right moment? Of course I could do that by recording video + audio, but that would result in humongous files. Thank you for any advice.