How do I create this 'build' effect?

Questions about producing? Ask them here.
https://youtu.be/bM7SZ5SBzyY?t=35
https://youtu.be/AOeY-nDp7hI?t=17

In these two parts of these tracks, there is a 'building' effect in the main instrument. How can this be done?

I've experimented with things such as increasing a Lowpass filter, and increasing Decay time, but neither so far has really hit it on the dot with this.
Try using the “moog” filter and turning the cutoff frequency up.
SkyEyeMCCIX wrote:
Fri Sep 29, 2017 9:04 pm
https://youtu.be/AOeY-nDp7hI?t=17
theres a lot going on -When you ask Qs like this, You need to add exact timestamps for where the wanted sound starts and less important -ends
Like @2:32 -> 2:55

But if you mean 0:59, then its a highpass filtered part