The answer is an altimeter it measures altitude and altitudes definition is height
In the text it says, "She taught me my scales and exercises, too, on the little parlor organ", "I struggled with the 'Harmonious Blacksmith'", and "<span>I had been doggedly beating out some easy passages from an old score of 'Euryanthe'". The boy mostly practiced scales and exercises, but he also played "Harmonius Blacksmith" and "Euryanthe".</span>
