ラジオを合わせる
synchronize the sound with the picture
sing (along) to the [somebody's] piano(‐playing)
読み方 あわせる
1
(=加える)to combine, unite, join, put together, add up, sum up (two or more things)
2
(=適合せしむ)to fit, suit, adapt, adjust, conform, square (one thing to another)
3