I think that teachers of online classes would want to give their students audio feedback to help develop a connection to their students Audio recordings can be done with software on most all computers. The recording could be linked in an email to each student and comments and/or suggestions could be made individually to meet students’ needs.
Another option for digital feedback is Evernote. It is a great way to give students digital feedback and its free!
A third option would be to post an image in a student’s email. There are literally thousands to choose from. Of course, I would only use this type feedback for positive notes.
source: google images