While valid, this classification is widely seen as inadequate. Rather, it may be more informative to describe percussion instruments in regards to one or more of the following four paradigms:  Many texts, including "Teaching Percussion" by Gary Cook of the University of Arizona, begin by studying the physical characteristics of instruments and the methods by which they can produce sound. This is perhaps the most scientifically pleasing assignment of nomenclature whereas the other paradigms are more dependent on historical or social circumstances. Based on observation and experimentation, one can determine how an instrument produces sound and then assign the instrument to one of the following four categories:  "Idiophones produce sounds through the vibration of their entire body." Examples of idiophones:  Most objects commonly known as drums are membranophones. Membranophones produce sound when the membrane or head is struck with a hand, mallet, stick, beater, or improvised tool. Examples of membranophones:   Most instruments known as chordophones are defined as string instruments, wherein their sound is derived from the vibration of a string, but some such as these examples "also" fall under percussion instruments. Most instruments known as aerophones are defined as wind instruments such as a saxophone whereby sound is produced by a stream of air being blown through the object. Although most aerophones are played by specialist players who are trained for that specific instrument, in a traditional ensemble setting, aerophones are played by a percussionist, generally due to the instrument's unconventional nature. Examples of aerophones played by percussionists   When classifying instruments by function it is useful to note if a percussion instrument makes a definite pitch or indefinite pitch. For example, some percussion instruments such as the marimba and timpani produce an obvious fundamental pitch and can therefore play melody and serve harmonic functions in music. Other instruments such as crash cymbals and snare drums produce sounds with such complex overtones and a wide range of prominent frequencies that no pitch is discernible. Percussion instruments in this group are sometimes referred to as pitched or tuned. Examples of percussion instruments with definite pitch:  Instruments in this group are sometimes referred to as non-pitched, unpitched, or untuned. Traditionally these instruments are thought of as making a sound that contains such complex frequencies that no discernible pitch can be heard. In fact many traditionally unpitched instruments, such as triangles and even cymbals, have also been produced as tuned sets.