The aulos (Greek αυλός, plural αυλόι, auloi) or tibia (Latin) was an ancient Greek musical instrument. Different kinds of instruments bore the name, including a single pipe without a reed called the monaulos (μόναυλος, from μόνος "single"), and a single pipe held horizontally, as the modern flute, called the plagiaulos (πλαγίαυλος, from πλᾰγιος "sideways"), but the most common variety must have been a reed instrument. Archeological finds and other evidence indicate that it was usually double-reeded, like an oboe, although simple variants with a single clarinet reed cannot be ruled out.
