Joan, I had another thought.

A song should not have the same emotion throughout. The same song can be gentle, and the middle of that same song it may get stronger, and the ending go back to where it started.
You can bring that emotion out with volume, number of instruments, and raising the key.

A singer might start in a key that is low for him/her. As the song is transposed higher, his voice begins getting more comfortable. By the end of the song the volume is up, everybody is playing, and the singer is in his best key sounding stronger than ever.

One more thought---try to transpose the song to a key that's slightly higher or lower that the one you start in--unless you have a special reason.

The bad part of using the transposer button is that you lose the oppertunity to play in the other keys. I have a friend that after learning a song in the original key, he then learns to play the same song in all the possible keys. What a command of the instrument he has.
I hope this helps. John C.