Final answer:
A 'group of two or more pitches sounding at the same time' is defined as harmony. It is distinct from melody, rhythm, and tempo. Timbre describes the unique quality of a sound that distinguishes different sources of sound.
Step-by-step explanation:
According to Professor Wright, a "group of two or more pitches sounding at the same time" is a basic definition of harmony. This differs from melody, which refers to a sequence of notes that are perceived as a single entity. Harmony adds depth to melodies by creating chords and simultaneous sounds.
Rhythm, on the other hand, is the pattern of beats or a sequence of sounds and silences in time, while tempo is the speed at which a piece of music is played. Timbre is a characteristic of sound that allows us to distinguish different types of sound production, such as instruments, even when they are playing the same pitch at the same loudness.
It involves the complex interaction of frequency, amplitude, and timing of sound waves. On the other hand, loudness of sound is described by the term 'intensity level' or 'decibel', and is not to be confused with frequency or pitch, the latter describing the highness or lowness of a sound.