Offertoire funèbre

The sheet music indicates to play the introductory chords with tremolo. But I found I couldn't play all the way through the introduction without my hand becoming fatigued, which I think is a problem related to the fact that I have so much tension in my hands and arms when I play. I'm trying to fix that, but it's really a tough habit to break, and it's hard for me to fully relax. However, I think the piece still works, even if not totally accurate.