The Hornbostel-Sachs system of musical instrument classification defines chordophones as all instruments in which sound is primarily produced by the vibration of a string or strings that are stretched between fixed points.
They include the piano therefore, as well as other kinds of zithers such as the koto, and musical bows.
311.1 Musical bows - The string bearer is flexible (and curved).
311.11 Idiochord musical bows - The string is cut from the bark of the cane, remaining attached at each end.
311.111 Mono-idiochord musical bows - Containing one string only 311.112 Poly-idiochord musical bows or harp-bows - Containing several strings that pass over some type of bridge.
311.12 Heterochord musical bows - The string is of separate material from the bearer.
311.211 Instrument has one resonator gourd 311.22 True stick zithers - Round sticks which happen to be hollow by chance do not belong on this account to the tube zithers, but are round-bar zithers; however, instruments in which a tubular cavity is employed as a true resonator, like the modern Mexican harpa, are tube zithers.
312.2 Half-tube zithers - The strings are stretched along the convex surface of a gutter.
314.122 With resonator box - the piano is part of this subdivision.
The strings are stretched across the mouth of a trough 315.1 Without resonator.
- Gusli The strings are stretched across an open frame 316.1 Without resonator.
The plane of the strings runs parallel with the resonator's surface.
321.1 Bow lutes - Each string has its own flexible carrier.
Notched bridge These instruments may be classified with a suffix, based on how the strings are caused to vibrate.