public function invert() {
		$func = function($n){return 11 - $n;};
		$this->tones = array_map($func, $this->tones);
	}
public function invert() {
		$func = function($n){return 11 - $n;};
		$this->tones = array_map($func, $this->tones);
	}
public function invert ( ) { $ func = function ( $ n ) { return 11 - $ n ; } ; $ this -> tones = array_map ( $ func , $ this -> tones ) ; }
inverts the pitches; eg 11 becomes 0, 10 becomes 1 etc.
@return [type] [description]
inverts the pitches ; eg 11 becomes 0 10 becomes 1 etc .