Pitch
Higher/lower. Children often mix up 'high' and 'low' with 'loud' and 'quiet'. The numbers on volume controls - a higher number representing a louder sound - add to the confusion! Other difficulties sometimes arise from moving to the right to go higher on a keyboard, and vice versa. When you think about it, these confusions are perfectly understandable and even rational: to a young child, 'high' and 'low' are vertical measurements.

Pitched and Unpitched Percussion
Percussion instruments are usually labelled either 'pitched' or 'unpitched'. 'Pitched' percussion instruments are those which are tuned to different pitches, to the extent that you can play a tune on them. Examples include xylophones, glockenspiels, metallophones and chime bars. 'Unpitched' percussion instruments are generally not tuned to a specific pitch: examples are some drums, tambourines, castanets and maracas. Be warned, though, that classification of this kind is not a precise science! Most instruments, even unpitched, will give out some kind of pitch when struck and others such as kettle-drums (timpani) are tuned according to the requirements of the piece of music they are needed for. Nevertheless, these descriptions can still be helpful.

Poly-rhythm
Layers of rhythm with different or opposing rhythms or metres played together or over each other.