micro:bit board doesn't have buzzer. If you want to make micro:bit sound you need to add external speaker or buzzer. Buzzer is integrate on micro:bit expansion board, you just need to inset micro:bit to expansion board.
You can also connect external buzzer/speaker if you want. micro:bit pin out music pin to P0.
The blocks in Musci class can be used to control music note and tone. It also has some musics already.
Create a new project, drag start melody block to on start. Choose a music and repeat times. You can choose ...in background to make music play in background.
【Note】sound is generated by shaking of object. People shaking our vocal cord in different frequency to speak. Buzzer work in same way, it sounds when get high/low level with different frequency from control board. To change the music tone you can change the sound.
Using ring tone block, we can simulate piano by setting different tones.
Using play tone block, buzzer can sound tones as setting.
This code makes buzzer repeating music notes do, re, mi, fa, sol, la and si.
Here we use A and B buttons to control the buzzer.
Press A or B buttons, the buzzer will sound different.