There are several ways you can do this:
– Build up like you describe until about 10 minutes or so before the end when you introduce a couple of more emotional closing tracks
– Build up to peaks every 20 minutes then slow down, rinse and repeat
– Mix using a different common thread and vary BPM throughout: tempo is not the only energy in a track of course, you can link tracks of varied BPMs and still build up energy. This takes some experience and knowing your tunage well. You can link tracks on feelings and the vibe they give off rather than technical mixing using BPM & key.
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