by Roderic Knight, Oberlin College, 2010

Organology, or the scientific study of musical instruments, has ancient roots. In China, a system of classification known as the pa yin or "eight sounds" was devised in the third millennium BCE. It was based on eight materials used in instrument construction (but not necessarily in sound production) and allied to other physical and metaphysical phenomena. More recently, but still in ancient times, the Indian sage Bharata outlined in his Natyashastra (ca. 200 CE) a classification based on how the sound is produced: by blowing (sushira), setting a string in motion (tata), hitting a stretched skin (avanaddha), or hitting something solid (ghana). This system endures as a worldwide phenomenon today because Victor Mahillon adopted it for his catalog of the instruments in the Brussels Conservatory museum in the 19th century, and because his system was picked up in turn by Erich M. von Hornbostel and Curt Sachs in producing their seminal Systematik der Musikinstrumente in 1914.

Hornbostel and Sachs sought to universalize the Mahillon catalog by developing a hierarchy of terms that could encompass all the methods of sound production known to humankind. They used three of Mahillon's terms: aerophone, for the "winds and brass" of the orchestra and all other instruments that produce a sound by exciting the air directly; chordophone, for all stringed instruments (including the keyboards); and membranophone for drums. Hornbostel and Sachs replaced Mahillon's fourth term, autophone (for instruments whose body itself, or some part of the body, produces the sound the Indian ghana type), with their newly coined term, idiophone, to avoid the ambiguous implication that an "autophone" might sound by itself.

In Hornbostel-Sachs, an instrument is assigned a number. It may be a single digit, such as 1, indicating nothing more than the broad class, such as idiophone. More typically, an H-S number might have from two to nine or more digits (separated every three by a decimal point), to provide the degree of specificity needed to distinguish it from another instrument. The numbering method is based on the Dewey Decimal System, in use by libraries at the time.

Although Hornbostel-Sachs is the most widely used method for classifying instruments, applied by museums worldwide, translated into English in 1961, and taught regularly, it is also fraught with problems that have been tackled by many scholars over the century since its introduction. With this musical instrument collection, the latest reworking of Hornbostel-Sachs is introduced. It is called the Knight System, and it grew, as did Mahillon's, out of cataloging the collection. The four H-S terms are retained, with a fifth (coined by Francis W. Galpin in 1937), electrophone, added. In the Knight System, instruments are assigned a number, but because the internal subdivisions of the classes have been largely reworked, the numbers do not match the H-S numbers. To assure the two are never confused, the K-S number begins with a letter, as follows:

  • Y for Idiophone (Y is used for I to avoid resembling a Roman numeral I) - a solid or hollow body produces the sound
  • M for Membranophone - a stretched membrane or diaphragm produces the sound
  • C for Chordophone - a stretched string produces the sound
  • A for Aerophone - the air itself is set in motion
  • E for Electrophone - electric or electronic circuits produce the sound

A Knight System number has been applied to each instrument in the collection. An overview of the system is presented below. For the complete system and an explanation of suffixes used with the K-S numbers, please refer to the full document at the following website:

Overview of the Knight System for Musical Instrument Classification

See the PDF version of the chart here

Y  Idiophones

M13 Two heads

A  Aerophones

Y1 Concussion

    1 Vessel

A1 Ambient air

    1 Plaque

    2 Frame

    1 Beating

    2 Bar

M2 Shaken

    2 Slicing

    3 Dish

    1 Opposed hemispheres     3 Ribbon

    4 Vessel

    2 Hourglass

A2 Enclosed

Y2 Struck

    3 Frame

    1  Flute

    1 Plaque

M3 Friction

       1 Vessel flute

    2 Bar

    1 One head

          1 No duct

    3 Vessel

    2 Two heads

          2 Duct

Y3 Stamped

M4 Sympathetic

          3 Duct + chamber

    1 Solid

         2 Vertical flute

    2 Globe

C  Chordophones

          1 No duct

    3 Tube

C1 Variable tension

          2 Duct

    4 Split

    1  No neck

       3  Oblique flute

Y4 Shaken

    2 Single neck        4  Transverse flute

    1 Vessel

    3 Forked neck

       5  Double-layer whistle

    2 Sliding          

C2 Musical bow

    2  Reed

    3 Sheet

    1 Mouth resonated

       1  Free (hard) reed

    4 Concussion

    2 Gourd resonated

          1 Mouth blown

    5 Sympathetic

C3 Pluriarc or bow-lute

          2 Bellows blown

Y5 Scraped

C4 Harp

          3 Transverse

    1 Organic

    1 Strings-over

       2  Beating (soft) reed

      1 Wood

      1 Forked

          1 Conical bore

      2 Gourd

      2 Spike

             1 Single reed

    2 Manufactured

        1 Curved neck

             2 Double reed

      1 Metal

        2 Straight neck

          2 Cylindrical bore

      2 Cloth

         (Bridge harp)

             1 Single reed

      3 Sandpaper

    2 Strings-in

             2 Double reed

Y6 Friction

      1 Arched

             3 Multiple reed

    1 Solid

      2 Angled

    3  Horn (lip-reed)

    2 Vessel

C5 Zither

       1  Limited register

Y7 Plucked

    1 Stick

          1 Fixed length

    1 Frame

    2 Tube

          2 Variable length

    2 Board

    3 Raft

       2  Multiple register

Y8 Blown

    4 Trough

          1 Fixed length


    5 Box

          2 Variable length

M  Membranophones

    6 Harp zither

             1 Fingerhole

M1 Struck

    7 Frame

             2 Slide

    1 One head, open

C6 Lute

             3 Valve

      1 Vessel

    1 Plucked

    4  Corrugated pipe

      2 Frame

      1 One piece

       1 Twirled

    2 One head, closed

      2 Multi-part

       2  Blown

      1 Deep

    2 Bowed

A3 Plosive aerophone

      2 Shallow

      1 One piece

    1 Open


      2 Multi-part

    2 Enclosed


C7 Lyre