Designed by Toshio Iwai and Yu Nishibori, a Tenori-On is a handheld digital interface/instrument for performance and composition. The device main screen is a grid of touch sensitive buttons which will light up when pressed and play a sound when passed over by a line of lights indicating the tempo and current position of the piece. Each row of buttons corresponds to a specific pitch with their position indicating when they will be played in relation to the tempo set by the musician. The instrument builds upon Toshio Iwai's earlier work such as Electro Plankton for the Nintendo DS. Below is an product demonstration of the Tenori-On displaying its capabilities.

The Tenori-On have become increasingly more popular and often featured in concerts and live performances, such as:

English comedian Bill Bailey occasionally uses this instrument in his live performances including his 2009-2010 world tour; it is featured in Dandelion Mind.
UK electronic singer Little Boots is also known for using a Tenori-On for live performances.
Björk has used a Tenori-on in her live performance of the song Who Is It on Voltaic tour.
Jon Hume from New Zealand band Evermore has a Tenori-On built into his silver Gibson guitar used on-stage during the Truth of The World and subsequent tours.
Gotan Project on tour 2010/2011.
Mexican electronic music act Nortec Collective Presents Bostich + Fussible
Jonathan Coulton frequently uses a Tenori-On when performing his song My Monkey

Here's a performance of Little Boot's Hot Chip Tenori On cover.

A solo performance from the creator of the Tenori-On, Toshio Iwai.