Information:  - Biologically, a child (plural: children) is a human being between the stages of birth and puberty. The legal definition of "child" generally refers to a minor, otherwise known as a person younger than the age of majority.  - A toy is an item that is generally used for children's play. Playing with toys is supposed to be an enjoyable means of training young children for life in society. Different materials like wood, clay, paper, and plastic are used to make toys. Many items are designed to serve as toys, but goods produced for other purposes can also be used. For instance, a small child may fold an ordinary piece of paper into an airplane shape and "fly it."  Newer forms of toys include interactive digital entertainment. Some toys are produced primarily as collector's items and are intended for display only.   - A glockenspiel (or , "Glocken": bells and "Spiel": game) is a percussion instrument composed of a set of tuned keys arranged in the fashion of the keyboard of a piano. In this way, it is similar to the xylophone; however, the xylophone's bars are made of wood, while the glockenspiel's are metal plates or tubes, thus making it a metallophone. The glockenspiel, moreover, is usually smaller and higher in pitch.  - Wood is a porous and fibrous structural tissue found in the stems and roots of trees, and other woody plants. It is an organic material, a natural composite of cellulose fibers which are strong in tension embedded in a matrix of lignin which resists compression. Wood is sometimes defined as only the secondary xylem in the stems of trees, or it is defined more broadly to include the same type of tissue elsewhere such as in the roots of trees or shrubs. In a living tree it performs a support function, enabling woody plants to grow large or to stand up by themselves. It also conveys water and nutrients between the leaves, other growing tissues, and the roots. Wood may also refer to other plant materials with comparable properties, and to material engineered from wood, or wood chips or fiber.  - The Pixiphone was a range of toy glockenspiels ( although they were inaccurately labelled as xylophones on their packaging ) . The larger Pixiphones had a ' raiser - bar ' which could be used to end a note abruptly , rather than letting it fade naturally . Although marketed as a children 's toy , the Pixiphone could be tuned pitch - perfect and was very robust , resulting in many children using them at British schools .  - Clay is a fine-grained natural rock or soil material that combines one or more clay minerals with traces of metal oxides and organic matter. Clays are plastic due to their water content and become hard, brittle and nonplastic upon drying or firing. Geologic clay deposits are mostly composed of phyllosilicate minerals containing variable amounts of water trapped in the mineral structure. Depending on the soil's content in which it is found, clay can appear in various colours from white to dull grey or brown to deep orange-red. Although many naturally occurring deposits include both silts and clay, clays are distinguished from other fine-grained soils by differences in size and mineralogy. Silts, which are fine-grained soils that do not include clay minerals, tend to have larger particle sizes than clays. There is, however, some overlap in particle size and other physical properties. The distinction between silt and clay varies by discipline. Geologists and soil scientists usually consider the separation to occur at a particle size of 2 µm (clays being finer than silts), sedimentologists often use 45 m, and colloid chemists use 1 m. Geotechnical engineers distinguish between silts and clays based on the plasticity properties of the soil, as measured by the soils' Atterberg limits. ISO 14688 grades clay particles as being smaller than 2 m and silt particles as being larger.  - The xylophone (from the Greek words "xylon", "wood" + "phn", "sound, voice", meaning "wooden sound") is a musical instrument in the percussion family that consists of wooden bars struck by mallets. Each bar is an idiophone tuned to a pitch of a musical scale, whether pentatonic or heptatonic in the case of many African and Asian instruments, diatonic in many western children's instruments, or chromatic for orchestral use.    Given the information, choose the subject and object entities that have the relation of 'subclass of'.
The answer to this question is:
pixiphone , idiophone