Explanatory diagrams
The occassional diagram, indicated by a soft chime of the audio player, opens up audio for topics like math, architecture, graphic design, computer science, gardening and DIY surgery tips and tricks.
This way we can avoid the dreaded words... "Please see accompanying PDF" or "Go to our website to see..." or "Just Google such and such"...
Instead, let's get those illustrations right in the player app, using Timeline Notation.