Very good choices Kiwi. I adore the piece Harnessing anger and the scene was so powerful. I think it's actually the scene I've rewatched the most. I don't know if you noticed but 2 of my favorite piece have a small part of Harnessing anger in it : saving her sister and the ark from S2 and drowning from S3. Often, when Supergirl pushes her limits to the extremes, Mr Neely includes this part.
About the piano part, there are 2 songs that I listen over and over : I'm so proud of you (S2)... this was a sad and emotional scene between Alex and Kara after Kara sent Mon-El away in her pod. Also, in S1, when Alex confesses about killing Astra, that was another incredible moment. The song playing was : afraid of losing you.
Thanks for the link for Blake's music.