I used to work as a music producer way back in the day. And back then, I was always looking for new and inventive ways to make audio effects. I do recall one time I had this very unusual thought. I was wondering what it would sound like to put a vocal through the heating and cooling ductwork for reverb effect. Yes, I know it sounds strange. But, I still wanted to see if the sounds of singing or speaking through the air ducts of a heating and cooling system would work. I figured because of the hollow space of the air ducts through the ductwork, it may create an original sound. I decided to try this one day with my own voice just speaking through the microphone. Then, I fed the audio through the ductwork instead of the speakers in the studio. The sound was actually pretty flat sounding. Singing through the heating and air conditioning ductwork was not going to be something to explore. While I was up there in the ductwork removing all the equipment from my test, I noticed it was dirty in there. This actually made me tell the studio owner to call his local heating and cooling company to get the ductwork cleaned. I did know a little bit about HVAC systems and how they worked. If that ductwork remained dirty, it could clog up the heating and air conditioning system. This could turn into a major expense. Especially for a recording studio! The owner of the place actually took my advice. He also gave me a discounted rate in return the next time I recorded there.