Definition of "allegretto"

It was only after the conception had received its fullest due, and the vast and complex organism its perfect development, that the certainty arose of an effect on human emotion comparable to that which was born when the opening bars of the allegretto in Beethoven's Seventh Symphony had been played for the first time, and the idea of them was from that moment alive and abroad in the world.

1880, Edmund Gurney, The Power of Sound, page 99