Whilst the occasion for sounding "Taps" is the same as for "Last Post", the tunes are quite different. Taps is the 'easier' tune of the two, as evidenced by the fact that I had mastered this tune on the bugle (in the days before a bicycle accident robbed me of some front teeth and ended my career as a brass player), whilst I was still struggling to manage "Last Post."

The story behind it sounds reasonable, too.