Double-click the desktop icon for the digital audio interface to which the drums are recorded, for example Pro Tools or Logic.
Open the relevant session. Click "File," "Open Recent" and select the session from the drop-down menu.
Click the first drum channel down from the top to highlight it. Name each channel so you know which is which when mixing. If you haven't done this, to determine which audio channel is which, hit "Play" and use the "Solo" on each channel button. Listen to each and name the channel accordingly.
Click "Send To" and select "Bus 1." In audio, a bus is a mix channel to which you can route multiple channels. Bus mixing enables you to control multiple audio recordings with one set of controls. If this bus channel is grayed out, use the next available one.
Highlight the remaining drum tracks and send each one to "Bus 1."
Click on "Bus 1" to highlight it. This assigns subsequent edits to all audio in the channel.
Open the "Effects" menu. The exact process for doing so varies according to which program you use, but this menu is typically located in the top-left of the interface. Select "Compression" from the drop-down menu.
Set the "Threshold" dial to 80 percent. Compression tempers the volume peaks that naturally occur in a sound recording. By setting the threshold to 80 percent, any sound in the loudest 20 percent will be compressed to be quieter.
Set the "Ratio" dial to 4:1. This means any sound in the loudest 20 percent of the drum mix reduces in volume to four times less than its original volume.
Hit "Play" to hear your next adjustment in real time.
Adjust the "Output" gain dial on the compressor to boost the drum volume. Compressing something that is too quiet may seem counterintuitive, but by limiting the dynamic range of the drums, you create more scope for boosting the quietest part of the sound. Without compression, you'd need to boost the volume to distorted levels in order to make the very quiet parts audible.