How to reach an item in an Array

i created a number of classes that contain animation and a button to start the animation. and i am loading them into an array.
and i need to know when the last array item was pressed . so i tried to add an eventlistener to the Array in the last place like this:

_notes[12].addEventListener(TouchEvent.TOUCH, playNext);

but it doesnt recognize it. i tried every think i could think of…
can anybody assist me?