Significats de parenthetical expression en anglès

How would you naturally vary the pitch in introducing an explanatory or parenthetical expression like the following:

When a parenthetical expression comes between a pronoun in the nominative case and its verb, the objective is often incorrectly used instead of the nominative.

Parenthetical expressions, also for the same reason, are read in lower pitch.

The parenthetical expressions would really not be needed to supplement the emphatic words.