Reverb’s great for adding atmosphere and depth to your tracks; however, too much reverb on the lower frequencies quickly makes audio sound muddy. To prevent this, set up the reverb on a return track, then filter out the low frequencies before they can reach the reverb.
Here’s a simple piano line without reverb:
The same piano line, this time sent to a return track with a hall reverb on it:
Notice how the lower frequencies sound muddier now, especially at the beginning of the clip. Put a high-pass filter on the return track, before the reverb:
Because the filter’s in front of the reverb on the return channel, only the high frequencies are reverberating, and the low frequencies stay “dry.”