1 low pitch

2 quiet (voice)

3 subdued

4 low-key

5 low-profile

1 to coordinate

2 to harmonize

3 to fit together

4 to match (colors etc)

5 harmonious

6 concerted

1 to cultivate

2 to train

3 to groom

4 training

1 to emphasize (a statement)

2 to stress

1 sentiment

2 tone and mood

3 taste

1 to sing the high part

2 to speak fine sounding but empty words (idiom)

1 monotonous

2 dull

3 tedious (idiom)

1 to speak with a foreign accent or using words from a foreign language (usually derogatory) (idiom)

1 to play the same old tune (idiom); unoriginal

1 replaying the same old tunes (idiom); conservative, unoriginal and discredited

2 to keep harping on about the same old stuff