If the music is played outside and the music is loud, the other party will hear it. If the music is low or you listen to music and make QQ calls with headphones, the other party can't hear you.

how to use QQ phone:

open the chat window with friends

at the far right of the line below the text input field, click the plus sign icon

The first icon is QQ phone, and you can talk to friends by clicking it

Note: it is best to talk to friends in WiFi environment, otherwise a lot of mobile phone traffic will be used.