A steel guitar (Hawaiian: kīkākila) is any guitar played while moving a steel bar or similar hard object against plucked strings. The bar itself is called a "steel" and is the source of the name "steel guitar". The instrument differs from a conventional guitar in that it does not use frets; conceptually, it is somewhat akin to playing a guitar with one finger (the bar). Known for its portamento capabilities, gliding smoothly over every pitch between notes, the instrument can produce a sinuous crying sound and deep vibrato emulating the human singing voice. Typically, the strings are plucked (not strummed) by the fingers of the dominant hand, while the steel tone bar is pressed lightly against the strings and moved by the opposite hand.
The idea of creating music with a slide of some type has been traced back to early African instruments, but the modern steel guitar was conceived and popularized in the Hawaiian Islands. The Hawaiians began playing a conventional guitar in a horizontal position across the knees instead of flat against the body, using the bar instead of fingers. Joseph Kekuku developed this manner of playing a guitar, known as "Hawaiian style", about 1890 and the technique spread internationally.
The sound of Hawaiian music featuring steel guitar became an enduring musical fad in the United States in the first half of the twentieth century and in 1916, recordings of indigenous Hawaiian music outsold all other U.S. musical genres. This popularity spawned the manufacture of guitars designed specifically to be played horizontally.