Page "Pitch accent" Paragraph 1

Proto-Indo-European accent is usually reconstructed as a free pitch-accent system, preserved in Ancient Greek, Vedic, and Proto-Balto-Slavic.

The Greek and Indic systems were lost: Modern Greek has a pitch produced stress accent, and it was lost entirely from Indic by the time of the Prākrits.

Balto-Slavic retained Proto-Indo-European pitch accent, reworking it into the opposition of " acute " ( rising ) and " circumflex " ( falling ) tone, and which, following a period of extensive accentual innovations, yielded pitch-accent based system that has been retained in modern-day Lithuanian and West South Slavic languages ( in some dialects ).

Some other modern Indo-European languages have pitch accent systems, like Swedish and Norwegian, deriving from a stress-based system they inherited from Old Norse, and Punjabi, which developed tone distinctions that maintained lexical distinctions as consonants were conflated.