Update January 17, 2020: The Xtone database is no longer available.
Larry Hyman's Cross-Linguistic Tonal Database (XTone) is a web-accessible forum developed at Berkeley to which interested researchers worldwide can contribute basic descriptive characterizations of as many tone systems as possible, with the goal of discovering new language-specific and cross-linguistic tone patterns. While tone is known to be especially prevalent in Subsaharan Africa, East and Southeast Asia, and parts of New Guinea, Meso-America and Amazonia, languages with tonal contrasts are found in almost all parts of the globe. The database has been organized to highlight four aspects of tone systems: inventories of tones and tone-bearing units; inventories of tone alternations; inventories of the tonal melodies found within grammatical domains of different sizes; interactions of tone with other phonological properties.