David Sossa gives a lesson on humidity and the classical guitar. He discusses humidity, how it affects the guitar, and ways to keep humidity levels even. This video comes via his YouTube channel. Living on the West Coast of Canada (I live on Vancouver Island), the humidity is actually too high at times so his mention of the two-way system is helpful. Also, the bluetooth device is pretty cool. The products he mentions are: D’Addario Humiditrak and the D’Addario Humidifier, and Two-Way Humidification System.