It's from an 11th century religious dialogue called the Elucidarium. You can find an edition here. The context is a discussion of predestination in Christian theology. The text goes (italics for bits not shown in the inked image):

Ex(plicatio). ...Qui etiam propter se ipsos iuste pereunt, cum malum sua sponte eligunt, diligunt et vellent sine fine vivere, ut possent sine fine peccare.

Q(uaeriti)o. Quare permittit Deus electos sine fine peccare?

Ex(plicatio). Ut patefaciat in eis divitias misericordiae suae.

Q(uaeriti)o. Salvantur praedestinati, si non laborant?

Ex(plicatio). Praedestinatio taliter est instituta ut precibus vel laboribus obtineatur...

Answer. ...Those who perish by rights through their own (deeds), since they choose evil of their own will, they love and would like to live without end, so that they may sin without end.

Question. Why does God permit those who are chosen to sin without end?

A. So that he may reveal the riches of his mercy in them.

Q. Are the predestined saved, if they do not perform works?

A. Predestination is such that it may be obtained by either prayers or works...

(You'll see from the edition I've linked that this manuscript has a textual variant: the "sine fine" in the first "quaeritio" is apparently a dittography from the previous line.)

Nothing to do with trumpets, I'm afraid! I wouldn't be surprised if an expert on mediaeval manuscripts were to tell me that the illustration is a result of the scribe finding the text unbearably pretentious. But I suspect a more likely reason is a custom of creating a contrast between the text and illuminations.