>>96069308Basically, upward compression increases the volume of the signal below the threshold.
Most compressors are standard compressors that offer ratios like 2:1, 4:1 etc which push the signal downward and make the compressed frequencies or transients quieter. An upward compressor instead makes those parts louder by utilizing a negative ratio such as 1:2. Compression is definitely one of the more mystifying parts of audio production, there's videos on youtube that explain the ins and outs far better than I ever could.
A bell curve in an EQ is the most standard shape when EQing; if you're using a parametric EQ, you'll be able to see that it looks like a hill or a dip, depending on whether you're boosting or cutting. If there's anything else you'd like the cymbal monkey in my head to try and explain, I'll try my best!
