Midrash as sermon.
In the last installment of this series we discussed the disagreement among scholars as to whether homiletical midrash may represent a transcription or adaptation of synagogue sermons delivered by tannaim and amoraim. We will not review the arguments for and against again; however, there is strong internal evidence, in my opinion, that suggests that at least some midrashic passageswere declaimed in public.
Aharon Yehoshua Itzhak Mirsky points out in his introduction to Midrash Tannaim  to Bareishis that dozens of passages in Midrash Rabbah are adapted to public discourse in form and structure and utilize rhythm, alliteration, word play and other poetic techniques. The implication of this finding is that they were delivered as sermons. Let us look at just a few of such passages.
The day is Yours, so is the night Yours (Psalms 74, 15).
The day praises You, the night praises You,
As day is in your power, so night is in your power,
When You perform miracles for us in the day, when You perform miracles for us at the night,
Yours is the day, So Yours is the night,
When You perform for us miracles in the day, we praise you in the day,
When Your perform for us miracles in the night, we praise you at night,
You performed for us miracles in the day and we said song for You in the day – “That day Devorah and Barak ben Avinoam sang…”.
You performed for us miracles at night and we said a song for You at night – “ This song will be for as the night on which a sacrifice is renewed”.
It is good to say sing for You in the day, it is good to say a song for you at the night.
Because you prepared the light and the sun and You made two great luminaries (Genesis Rabbah 6,2)
Another example from parshas Bareishis.
All trees as if they converse one with the other.
All trees as if they converse with human beings,
All trees were created to accompany human beings (Genesis Rabbah 2, 5)
Men of Name (Hashem) – R.Acha says, Disgraceful, also without a name, and you call them “men of Name??
But (the explanation is that hashem means destruction:)
They destroyed the world,
They were destroyed from the world,
They caused the world to be destroyed.
There are literally dozens of other examples. It is reasonable to suppose that they were originally written in a such manner so as to make them suitable for public delivery. This feature serves as an indication that there was a public audience for many such passages and that they represent a record of rabbinic sermons.