The basic idea of the Musar Movement was not at all connected with yeshivas originally. It was simply the realization that no one is automatically moral without learning. [Moral principles are included in what is called "universals." Things that apply to different particulars.And it is characteristic of universals that they are recognized by reason. One might need sense perception to understand the meaning of a universal, but it is reason that recognizes the principle as Michael Huemer goes into detail in his essay criticizing Ayn Rand.]
The insight of the Musar movement was the realization that the Rishonim [authors during the Middle Ages] had an extra measure of logical rigor in understanding the principles of the Old Testament and the two Talmuds as opposed to achronim[authors after the Middle Ages.]
[This is a well established fact even though I find it very hard to get into the Rishonim without the help of the Achronim on the Gemara.
But in terms of the basic principles of Torah, achronim go off on tangents far away from Torah. Sometimes they find some odd principle that appeals to them and they decide that that principle is what the whole Torah is all about. The examples are many. Sometimes the principles they come up with are in direct opposition to Torah and sometimes they are just some minor issue that that person want to exaggerate into some big deal.]
So even though in the Musar movement itself--the disciples of Reb Israel Salanter--they also wrote books explaining ethical principles of Torah but as a rule they are sticking with the approach of the rishonim. [That is until the second generation of Musar which then started also going off on tangents.]
The insight of the Musar movement was the realization that the Rishonim [authors during the Middle Ages] had an extra measure of logical rigor in understanding the principles of the Old Testament and the two Talmuds as opposed to achronim[authors after the Middle Ages.]
[This is a well established fact even though I find it very hard to get into the Rishonim without the help of the Achronim on the Gemara.
But in terms of the basic principles of Torah, achronim go off on tangents far away from Torah. Sometimes they find some odd principle that appeals to them and they decide that that principle is what the whole Torah is all about. The examples are many. Sometimes the principles they come up with are in direct opposition to Torah and sometimes they are just some minor issue that that person want to exaggerate into some big deal.]
So even though in the Musar movement itself--the disciples of Reb Israel Salanter--they also wrote books explaining ethical principles of Torah but as a rule they are sticking with the approach of the rishonim. [That is until the second generation of Musar which then started also going off on tangents.]