How does Danish glottalization correspond to word tones in Norwegian and Swedish?

In the Scandinavian languages, the relationship between Danish glottalization and the word tones found in Norwegian and Swedish is rooted in their shared linguistic history.

In most of Norway and Sweden, as well as in some scattered Danish dialects, there exists a special word tone (or pitch accent) system. This system distinguishes between words based on their historical origins: old monosyllables typically carry one type of pitch, while old polysyllables carry another.1

In standard Danish, however, this tonal system has been replaced by a phenomenon known as glottalization, or stød. This feature—a glottal modification of a vowel or consonant sound—functions in instances where Norwegian and Swedish utilize the first type of word tone. Essentially, the stød is a modern phonetic development derived from what was originally a tonal accent.12