The percussion instrument sub-category of the Idiophone family is classified by Hornbostel-Sachs as struck or friction idiophones. This also includes struck or friction , struck or friction membranophones or struck chordophones. Where an instrument meets this definition but is often or traditionally excluded from the term percussion this is noted.
a) Instruments commonly used as un-pitched and / or untuned percussion.
b) Instruments commonly part of the percussion section of a band or orchestra.
Note: These three groups overlap heavily, but inclusion in any one is sufficient for an instrument to be included in this list. However, when only a specific subtype of the instrument qualifies as a percussion instrument, only that subtype is listed here.
For example: A samba whistle [or apito] is an un-pitched percussion instrument, but a whistle in general is considered an aerophone.