How did Latin stress accent change from early Latin to Classical Latin?

In the development of the Latin language, the stress accent underwent a significant shift:

• Early Latin: The language featured a stress accent that consistently fell on the first syllable of a word.1
• Classical Latin: The accent moved away from the initial syllable. It typically fell on the penultimate (second to last) syllable, or, if that syllable was considered "light" in quantity, it shifted to the antepenultimate (third to last) syllable.1

While the exact nature of this Classical accent remains a subject of scholarly debate—with some suggesting it was a musical or tonal accent influenced by Greek models and others arguing it was a light stress accent—evidence indicates that in later Latin, this stress became increasingly heavy. This strengthening of the stress accent in the later period had profound effects on the language, contributing to the reduction, shortening, or loss of unstressed syllables and vowels, which ultimately helped shape the phonological evolution of the Romance languages.123