Another Beginner Error Question

Move the line into setup(), don't leave it at the top of the sketch (and start using code tags, the </> button):

int buttons[6]; // creates a global array with 6 elements, no values assigned

int notes[] = {262,294,330,349}; // global array with 4 elements, values assigned

void setup() {
  Serial.begin(9600);
buttons[0] = 2; // puts a value into one of the elements
}

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