The ottu (or otter) is a double reed wind instrument, used in Carnatic music of Southern India to provide a drone accompaniment to the similar nadaswaram oboe. Like the nadaswaram, the ottu is a large conical instrument, some two and a half feet long. Unlike the nadaswaram, the ottu has no fingerholes, being intended to produce one constant note while playing. It is provided with several small tuning holes which can be stopped with wax to modify its note. In some cases, a shruti box may be used in place of the ottu due to its steadier sound. The player holds the instrument in their left hand, sustaining the sound by inhaling through their nose, and with the right hand, beats on a drum strapped onto a belt.
- Sampa Ghosh; Utpal Kumar Banerjee (1 January 2006). Indian Puppets. Abhinav Publications. pp. 26–. ISBN 978-81-7017-435-6. Retrieved 25 December 2012.
- Shrine to Music Museum (University of South Dakota); Thomas E. Cross (1982). Instruments of Burma, India, Nepal, Thailand, and Tibet. Shrine to Music Museum, University of South Dakota. Retrieved 25 December 2012.
- Light Isaac (1967). Theory of Indian music. Printed at Shyam Printers. pp. 156–157. Retrieved 25 December 2012.
- Alison Arnold (2000). South Asia: The Indian Subcontinent. Taylor & Francis. pp. 360–. ISBN 978-0-8240-4946-1. Retrieved 25 December 2012.
- Vidya Shankar (1983). The art and science of Carnatic music. Music Academy Madras. p. 10. Retrieved 25 December 2012.
- Alison Arnold (2000). South Asia: The Indian Subcontinent. Taylor & Francis. pp. 359–. ISBN 978-0-8240-4946-1. Retrieved 25 December 2012.
- Images from The Beede Gallery: Shawms (Ottu and Nagaswaram), Southern India, ca. 1900-1940. National Music Museum, University of South Dakota.
- South Kensington Museum (1874). A descriptive catalogue of the musical instruments in the South Kensington Museum. Printed by G. E. Eyre and W. Spottiswoode. pp. 168–.