In these shiurim we completed the core analysis of the issue of proper speech on Shabbat. Many of the mekorot were pieced together in order to understand the comment of the Magen Avraham (307:11). The Magen Avraham here reads the rishonim (Ramban & Rambam vs. Rosh) as having a fundamental machloket about the type of speech that is forbidden on shabbat.
The key to this sugya is really a debate Bavli vs. Yerushalmi regarding the ways in which we are meant to limit our speech on Shabbat. The Bavli assumes that we are talking about speech related to activity that is forbidden on Shabbat. The Yerushalmi (Vayikra Rabba, Zohar) relate to a different notion of limiting speech on Shabbat only to tefila and talmud torah. This Yerushalmi find its way into the world of Halakha through the Tosafot, Sefer Chasidim and many of the chachmei ashkenaz. All of the mekorot can be seen at this link.
The first shiur was stopped at just a few minutes for technical reasons.