https://docs.arduino.cc/tutorials/uno-r4-wifi/adc-resolution/
In the code titled "This one for example plays the melody of Frere Jacques:"
Not too important, these lines are commented out, (information) but they are confusing for anyone who reads music.

67 // all the notes in this are sixteenth notes,
68 // which is 1/4 of a beat, so:

-They cannot all be sixteenth notes as some of them are longer than others in the code (and on the sheet music)
-The music was written in 4/4 time which makes 1 beat a quarter note, I don't think there are any sixteenth notes here.

Slowly say Frere Jacques... 4 beats 1 bar, these notes are quarter notes