How loud or quiet the music is.
Patterns of long and short sounds and silences, played over a steady pulse - the heartbeat of the music.
How a piece is put together: its sections, and the order they come in.
The tune: a line of notes that moves up and down in pitch.
Which instruments and voices are playing.
How many layers of sound there are, and how they fit together.
The colour of a sound: what makes a flute sound different from a violin playing the same note.
Whether the music sounds major or minor, and where its home - its Tonal Centre - is.
How fast or slow the music is.
Notes sounding together - chords - and how they move.