Using a voice recorder to listen to the lecture a second time is a great way to solidify the material. It can help to write the words of the lecture down and put these notes in a binder. This method requires great dedication but is very effective for learning. By the time the professor's words have been written down on paper, your mind has already processed the material three times. This is a great way to get
complete notes of the material, including the concepts spoken when your mind wanders during class, or even the material that was communicated while you were still taking notes on the previous concept. I did not realize how much my mind wandered during class until I started recording and listening to lectures.
I used a Sony Digital Voice Recorder during the years 2000-2004. The current models are unknown to me but at the time, the $300 model was well worth the cost. That voice recorder was more important to me than my computer, and I was a CS major.
Here is the
Sony Style webpage for their digital voice recorders.