Questions: What is "key" best defined as? a tonal center built on a tonic note and making use of a scale a symbol usually placed at the beginning of the music to tell the performer what note value is carrying the beat and how the beats are to be grouped the relative position, perceived high or low, of a musical sound the process in music whereby the tonal center changes from one tonic to another chords that change in a purposeful fashion beneath a melody

The answer is the first one: a tonal center built on a tonic note and making use of a scale.

Explanation for each option:

1. a tonal center built on a tonic note and making use of a scale - This is the correct definition of "key" in music. A key is essentially the group of pitches, or scale, that forms the basis of a music composition, centered around a tonic note.

2. a symbol usually placed at the beginning of the music to tell the performer what note value is carrying the beat and how the beats are to be grouped - This describes a time signature, not a key.

3. the relative position, perceived high or low, of a musical sound - This describes pitch, not key.

4. the process in music whereby the tonal center changes from one tonic to another - This describes modulation, not key.

5. chords that change in a purposeful fashion beneath a melody - This describes chord progression, not key.

Summary: The term "key" in music is best defined as a tonal center built on a tonic note and making use of a scale.