How to make a build-up: the filter sweep

Start with a low-pass filter almost closed so the music sounds muffled, then open it slowly over 8 or 16 bars. As more high frequencies come back, the music feels like it's rising and getting closer, and the drop hits harder when it opens all the way.

How to do it

1. Put a low-pass filter on the music bus (or the parts you want to build).
2. Set the cutoff around 200 to 400 Hz at the start of the build.
3. Automate it up to fully open over 8 or 16 bars.
4. Make the curve speed up towards the end.
5. Add a little resonance for a sweep you can hear, and stack risers or a snare roll on top.

Why it works

Brighter sounds feel closer and more intense. Opening a filter slowly makes a gradual change your ears can follow, so they expect something big at the end.