There are two important points to remember when learning to sing deeper.  You need to focus on your breathing and your posture.  Don’t simply breathe from your throat.  Take deep breaths, fill your lungs with air, and hold it.  This exercise will help to strengthen your diaphragm which is where your singing voice should come from; deep inside you, not just from your throat.  Another good exercise to practice is to inhale slowly and then exhale with an “ss” sound; like a snake hissing.  Exhale with the diaphragm, not the lungs.  The second point to remember is good posture.  When you exercise good posture the muscles that are responsible for voice projection are properly aligned.  This allows the chest to fully expand when you inhale.  Follow these simple rules and you will notice a change in the pitch of your voice.