Like Chroma, the music aspects are more an added benefit than a necessity. If you know music--like, really know music--you can sort of track the way the song is progressing and anticipate what'll happen next. However, you could ignore the music entirely or play with the sound off and have a totally fun shoot-em-up experience. Most of the time the synced music and visuals is more like watching Wizard of Oz with Dark Side of the Moon in the background than an actual skill-based benefit.
More important to victory is knowing when and how to use the game's Idol system. Poe has a trio (at least in the demo) of ghosts accompanying her journey. The Mercy ghost provides health, while the other two attack enemies. In order to use these ghosts you have to slot them into structures that appear during the level, typically two at a time, meaning you could set both structures to Mercy and get twice the healing benefit or set one to Mercy and one to an attack or both to attacks or whatever matches your style. Different-shaped structures also modify the ghosts, for instance making the Mercy ghost's healing power an area-of-effect versus an item pick-up.
Don't think just because you have these healing nodes that you're safe, though. I died untold numbers of times even with health freely available, and when the game's feeling really mean (during the boss battle) it takes away these nodes entirely and makes you focus solely on preserving Poe.
It's not Chroma, and I still think that's sort of a shame. However, A City Sleeps is some of the most fun I had at PAX, and definitely hooked me even if it was through mercilessly beating me down. And hey, I beat the demo in the end, so I think that's all that matters. As I said, look for A City Sleeps on Steam in October, for $15. You can preorder it now for a slight discount.
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