I was put on a weekly injectable dose, to give me a smoother slope into transition. That allowed my voice to deepen slowly rather than suddenly, which helped me retain my singing ability. As for the range difference, my full range shrunk but also dropped. Prior, I could sing a full soprano range down through the full alto. Currently I can sing the full baritone range up to mid-tenor. If I try to sing upper tenor my voice wobbles and cracks, although I'm only 4 months into my HRT so I'm not going to push it. When my voice eventually settles I'll re-train to ease my range open again.
Prior to my voice change I could sing in a lowish register but yeah, it just sounded like a female voice singing in a low register. After my voice changed, it really resonates and thrums--it feels different, it doesn't just sound different.