LB

You should have gone with “between grave and adagio” for the tempo clue. The answer is generally not faster than lento and is often considered “slower” in that it is more drawn out and broad when used than lento so conductors I’ve played under tend to go nearer to 40bpm for largo and 50-55 for lento on average (but the bmp is essentially the same, 40-60, one basically meaning slow, the other broad), so… yeah, hiccup that makes me think you only checked one source that doesn’t align with music textbooks. Sigma is completely new to me. It didn’t sound like an alpha, but that was the only thing I could think of in that context.