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A system for musical instrument classification by Roderic Knight, Oberlin College, 2015

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 (Classification of Musical Instruments) 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 3 to 6 digits, or as many as 9 or 10 (separated every three by a decimal point), to provide the degree of specificity needed to distinguish one instrument from another. The numbering method is based on the Dewey Decimal System, which was in common use by libraries at the time the system was devised.

Although Hornbostel-Sachs is the most widely used method for classifying instruments, applied to instrument collections 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. The system now includes a fifth term, coined by Francis W. Galpin in 1937, electrophone. The most current version of Hornbostel-Sachs, prepared in 2011 by the MIMO Consortium (Musical Instrument Museums Online), is available HERE.

The establishment in 2008 of the Roderic C. Knight Musical Instrument Collection at Oberlin College served as a catalyst for a new approach. It is called the Knight-Revision of Hornbostel-Sachs, or K-Rev for short. The four H-S terms are retained, as is the numbering system, 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, K-Rev numbers begin 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 blowing air into an object or moving it through the air produces the sound
  • E for Electrophone electric or electronic circuits produce the sound

The RCK Collection may be used to study K-Rev. A K-Rev number has been assigned to each instrument in the collection. A one-page overview of the system is presented below. To learn more, follow the link below to four items in downloadable pdf format:

  • Hornbostel-Sachs in the original German
  • The one-page overview below
  • This intro plus the one-page overview
  • The full 44-page Knight-Revision of Hornbostel-Sachs

The Knight-Revision of  Hornbostel-Sachs

Overview of the Knight-Revision of Hornbostel-Sachs (K-Rev)  © 2015 Roderic Knight

(Please use the pdf version in the link above for printing)


Y1 Concussion

   11  Plaque

   12  Bar

   13  Dish

   14  Vessel

Y2 Struck

   21  Plaque

   22  Bar

   23  Vessel

Y3 Stamped

   31  Globe
   32  Tube

Y4 Shaken

   41  Vessel

   42  Sliding

   43  Solid

   43.1 Sheet

   43.2 Spring

   44  Concussion

   45  Sympathetic

Y5 Scraped

   51 Organic

     (wood, gourd)

   52 Manufactured

      (metal, cloth,


Y6 Friction

   61  Solid

   62  Vessel

Y7 Plucked

   71  Frame

   72  Board

Y8 Blown

   81  Wood

   82  Metal

 Y9 Deformed

   91  Diaphragm

   92  Blade









M1 Struck

   11 One head, open

   11.1  Vessel

   11.11   Cylinder

   11.12   Cone

   11.13   Waisted

   11.14   Barrel

   11.15   Goblet

   11.16   Vase

   11.17  (other shapes)

   11.2  Frame

   11.21   Circular

   11.22   Polygonal

   12 One head, closed

   12.1 Deep (vessel)

   12.11   Cylinder

   12.12   Kettle

   12.13   Barrel

   12.2 Shallow (frame)

   13 Two heads

   13.1  Vessel

   13.11   Cylinder

   13.12   Cone

   13.13   Hourglass

   13.14   Barrel

   13.15   Ang. Barrel

   13.2  Frame

M2 Shaken

    21 External strikers

    21.1  Opposed


    21.2  Hourglass

    21.3  Frame

    22 Internal strikers

M3 Friction

    31 One head

    32 Two heads

M4 Sympathetic









C1 Variable tension

   11  No neck

   12  Single neck

   13  Forked neck

C2 Musical bow

   21  Mouth resonated

   22  Gourd resonated

C3 Pluriarc

C4 Harp

   41 Strings-over

   41.1  Forked

   41.2  Spike

   41.21  Curved neck

   41.22  Straight neck

              (Bridge harp)

   42 Strings-in

   42.1  Arched

   42.2  Angled

C5 Zither

   51  Stick or bar

   52  Tube

   53  Raft

   54  Board

   55  Box

   56  Trough

   57  Harp zither

   58  Frame

C6 Lute

   61 Plucked

   61.1  One piece

   61.2  Multi-part

   61.21 Neck attached

   61.22 Spike

   61.23 Half-spike

   62 Bowed

   62.1  One piece

   62.2  Multi-part

   62.21 Neck attached

   62.22 Spike

   62.23 Half-spike

C7 Lyre

   71  Bowl

   72  Box




A1 Ambient (Free)

   11 Slicing

   12 Beating (bull roarer)

   13 Whip (sonic boom)

A2 Blown

   21 Open

   21.1 Edge (flute)

   21.11 Vessel

   21.111  No duct

   21.112  Duct

   21.12 Vertical

   21.121  No duct

   21.122  Duct

   21.13  Oblique

   21.14  Transverse

   21.2  Chamber duct

   21.21  Simple

   21.22  Vented

   21.3  Corrugated pipe

   21.4  Siren (pulsated)

   22 Reed

   22.1 Free (Hard)

   22.2 Beating (Soft)

   22.21 Normally open

   22.211 Conical bore

   22.211.1  Single reed

   22.211.2  Double reed

   22.212 Cylindrical bore

   22.212.1  Single reed

   22.212.2  Double reed

   22.212.3  Free on pipe

   22.213 Mouthpiece only

   22.22 Normally closed

   22.221  Split or crushed

   22.222  Membrano-reed

   22.3  Ribbon Reed

   23 Lip reed

   23.1 Narrow compass

   23.11  Fixed length

   23.12  Variable length

   23.2 Wide compass

   23.21  Fixed length

   23.22  Variable length

     (fingerhole, slide, valve)

A3 Plosive 

   31 Closed

   32 Open