Your code falls through the first “if” statement because its time period has not yet passed.

It then starts to use startMillis_2, which is not yet initialized (and may be any value), in the next “if”.

Initialization of startMillis_2 only happens inside the first “if” statement but that code has not yet been executed.

The same goes for startMillis_3 and 4.

But I think there’s something more fundamentally wrong with your code. You execute all “if” statements inside of a loop that is continuously repeated. There is no sequence. You have to make sure that tone 2 can only be started after tone 1, etcetera.

Your code falls through (skips over) the first “if” statement in the output code because its time period has not yet passed.

It then starts to use startMillis_2, which is not yet initialized (and may be any value), in the next “if”.

Initialization of startMillis_2 only happens inside the first “if” statement but that code has not yet been executed.

The same goes for startMillis_3 and 4.

But I think there’s something more fundamentally wrong with your code. You execute all “if” statements inside of a loop that is continuously repeated. There is no sequence. You have to make sure that tone 2 can only be started after tone 1, etcetera.