Within the realm of open punctuation, some choices, particularly those related to the comma, are more subjective than objective. Some writers, for example, hear punctuation, and they use commas, semicolons, and colons to speed or slow the pace and rhythm of their prose. Aural punctuators tend to hear a comma as a one-beat pause, a semicolon as a two-beat pause, and a period as a three- or four-beat pause. Some also hear a colon as a pause; for others, a colon signals a sharp accelerando, a signal to speed ahead because something important is coming.
— The Copyeditor's Handbook
by Amy Einsohn