With Mote's Chrome extension installed you'll notice a little "Mote" icon in the Gmail composition menu whenever you open a message. Just click on that little icon and you can start recording a voice note that is then automatically inserted into your message. As I demonstrate in this short video, you can type above and below the inserted voice note.
Watch my short video about using Mote in Gmail to learn how to record and send a voice note. The video also shows how recipients can play your voice notes even if they don't have Mote installed in their web browsers.