Good quality delivery is absolutely dependent on the energy you put out to the audience. With strong breath support and vocal technique you can deliver your songs with the intensity appropriate for the message you are trying to convey. Your message should flow through you and to the listener. You want your notes to connect. Primary focus should be smooth movement throughout every phrase. Often, without good support the voice wobbles or is choppy and can distract the listener from the message. This smooth flow is called “legato”. It is a technique to learn and practice, however, just being conscious of it can make a difference. So start there.
My experience is that the key of the song is the biggest culprit for limiting the potential of its delivery. A common mistake with songwriters is to sing every song in the same key, or sing in low range because they think it is the most comfortable. I believe this is due in part to the writer not knowing their own vocal potential. For example, a slow song that’s melodic and intimate throughout is going to sound better in the low to mid range of the voice. The melody of a power ballad is usually written so that the chorus is anywhere from a third, to an octave higher than the verses. In this case, the singer should determine the key by the strongest notes/ words in the chorus. The strongest notes in the vocal range are usually upper-mid range, or “belting” range. High-energy songs are great with the choruses in the mid to upper-mid range throughout or with the verses in the mid range only.
Is this confusing enough yet? Are you thinking, “What is my low range, my mid range, my upper-mid range?” Well, there are general technical rules to explain this, but I prefer to explain it this way. Start by singing the very bottom note that you can hit. Find it on the keyboard or guitar and write it down. Then continue singing by half steps or whole steps. Your low range will have several notes. When you feel like you have to use a little more effort to sing a note, you are entering your mid range. Find this on the keyboard or guitar and write it down. When you again feel like you have to use a little more effort to sing a note, and you get louder you are entering your upper mid range. Write it down. When you reach very loud and feel you can’t go higher you are at the top of your upper mid range. If you keep going and your voice “flips over”, you have probably entered your head voice or lower high range. Notice that your head voice will get stronger if you continue going higher. The average singer should have about two octaves of total range. At least an octave and a half should be below the place where the voice “flips over”. The notes that you wrote down can assist you in deciding what key you want to sing a song.