This game is quite fun. I really like the way the combo mechanic is implemented. Having two options for the next combo input adds an extra layer of depth to the combat.
The music is great! It really fits the mood.
For sound effects, I'd love for there to be more auditory feedback in future versions if the game is developed further. I was really missing a 'player hurt' indicator sound and found myself dying because I didn't realize I had taken a few hits until I looked at the soul mete. I'd also suggest adding some input-trigger type sounds...something that provides auditory as soon as an attack input is registered like a small impact or low-end hit cut as close to the transient as possible to provide some immediate, audible timing feedback. The scythe sounds are great but the natural, slow attack of the sounds makes it hard to judge how your input is registering relative to the beat.
Overall, great game! I also really loved the soul pickup sounds...great design choice!