Editing Hornbostel–Sachs (section)

==Application of the system==
Beyond the top three groups are several further levels of classification, so that the [[xylophone]], for example, is in the group labeled 111.212 (periods are usually added after every third digit to make long numbers easier to read). A long classification number does not necessarily indicate the instrument is a complicated one. The [[Bugle (instrument)|valveless bugle]], for instance, has the classification number 423.121.22, even though it is generally regarded as a relatively simple instrument. The numbers in the bugle's classification indicate the following:
* '''4''' – an aerophone
* '''42''' – the vibrating air is enclosed within the instrument
* '''423''' – the player's lips cause the air to vibrate directly (as opposed to an instrument with a reed like a [[clarinet]], or an edge-blown instrument, like a [[flute]])
* '''423.1''' – the player's lips are the only means of changing the instrument's pitch (that is, there are no valves as on a trumpet)
* '''423.12''' – the instrument is tubular, rather than being a [[conch]]-type instrument
* '''423.121''' – the player blows into the end of the tube, as opposed to the side of the tube
* '''423.121.2''' – the tube is bent or folded, as opposed to straight
* '''423.121.22''' – the instrument has a [[Mouthpiece (brass)|mouthpiece]]

423.121.22 does not uniquely identify the bugle, but rather identifies the bugle as a certain kind of instrument which has much in common with other instruments in the same class. Another instrument classified as 423.121.22 is the bronze [[lur]], an instrument dating back to the [[Bronze Age]].