The document discusses historical comparative acoustics and prosodic typology in Tibetan dialects. It finds that peripheral non-tonal dialects preserve older consonant clusters corresponding to written Tibetan, while central innovative dialects developed tone and lost consonants over time. Analysis of disyllabic words finds pitch and pitch slope correlate with stress on the second syllable in non-verbs, reconstructing this as the Proto-Tibetan pattern. Intensity does not consistently signal stress. Fundamental frequency was thus a primary correlate of stress in Proto-Tibetan non-verbs.