R. Yonah: Shlomo attributes Musar to the heart, which is desire, like is explained in most places in the Sefer. Musar is Divrei Chachamim that obligate the listener to fix his deeds. When you hear Musar, bring your desire to it to fulfill it. Put your heart immediately to bring it to action. Whenever you hear Musar, contemplate if you lack that Midah, and agree in your heart to do it.

Malbim: Even if a person's ears received the laws of Chachmah from his Rebbeyim, there is no guarantee that he will go in them, for the images of desire contradict and fight with the laws of Chachmah. The heart, the power that rules in the body, has an inner war. Sometimes images of Chachmah rule over it, and sometimes images of desires, especially because the reasons for the laws of Chachmah are not known. Shlomo counsels to bring Imrei Da'as to your ears - to accept also Divrei Da'as, which are known via axioms and senses. They saw Hashgachas Hashem in His world, and how He arranged the world with Chachmah. He pays a Rasha according to his evil; in the end, the body dies. Via this, he brings his heart to Musar. He fears punishment, and has awe of Hashem's grandeur. This helps the heart to rule according to the laws of Chachmah and subdue desire.

R. Yonah: Shlomo attributes Imrei Da'as to the ears. Imrei Da'as is knowing words of Chachmah that do not obligate fixing deeds, just to become wise and know Divrei Chachmah. When you will hear them, bring them to your ears to hear them.

Malbim: Refer to 23:12:1:2