Some audio processing applications include a function to rescale the volume so that the maximum level in the recording is set to the peak value of the digital output.
Otherwise you may only be reaching half scale with the loudest sound in the recording.
Sometimes a recording can benefit from a little compression. This is where the loud sounds are brought down allowing the quiet ones to be brought up. It maintains a more consistent volume level throughout the piece. However some recording engineers overuse it, making the drums sound like smudges.