SOPP309: When was the organ introduced into the Christian liturgy?

Let’s start episode 309 of Secrets of Organ Playing Podcast. This question was sent by Michael and he writes: "Hi Vidas, You're very welcome! I very much enjoy your music scores, and I intend to purchase more in the future. Thank you for making them available for purchase! They are all excellent works. I was hoping you and Ausra might consider discussing the following organ history subjects in future podcasts: 1. When was the organ introduced into the Christian liturgy? Where were the first church organs installed (e.g. in which regions of Europe or Western Asia, etc)? How did the earliest organists serve in the context of the liturgy? Were the service-playing responsibilities quite different from that of a parish organist today? What was the medieval (pre-Tridentine) mass like? 2. Historical tunings/temperaments: Pythagorean tuning, Mean-tone temperament, the "well-temperaments," etc. When and were where these tunings were used? 3. Compositional practices/features of organ music prior to 18th century? Who were the key composers in the development of organ music composition from the medieval period to the 17th century? Thank you for your very helpful and informative podcast and blog posts! Most sincerely, Michael"