piano with arduino uno

int notes[]= {262, 294,330,349 }; // frequencies in Hz for do re mi fa fa


void setup() {
  // put your setup code here, to run once:
  Serial.begin(9600);

}

void loop() {
  // put your main code here, to run repeatedly:
  int keyVal = analogRead(A0);
  Serial.println(keyVal);
  if(keyVal >= 6 && keyVal<=9) { //pushing button 1
    tone(8,notes[0]);
  } else if(keyVal >= 510 && keyVal<=513) { //pushing button 2
    tone(8,notes[1]);
  }else if(keyVal >= 1000 && keyVal<= 1003) { //pushing button 3
    tone(8,notes[2]);
  } else if(keyVal == 1023) { //pushing button 4
    tone(8,notes[3]);
  } 
  else { //pushing nothing
    noTone(8);
  }

}

As I said before, I would add, for example, the note "sol" pushing for example button 3 and button 4 at the same time, but the value shown on the screen (thanks to the Serial.println) is the same of that of button 3, so it's impossible for me to associate a new value to the frequency of the note sol.

The schematic is in the attachment, if it's what you meant before.