A great way to increase your vocal abilities is to mimic animals and sounds in nature.
One of my favorite is the cat meow. We have a beautiful grey and brown tabby named Olive. I talk to her all of the time.
Another great one is the sulking puppy. Try to copy a puppy which is crying. They can get up pretty high.
Birds are great to imitate too. Try doing an eagle or hawk call. Coo like a dove or caw like a crow.
If you are really daring, have a go at acting like a crazy chimp or gibbon.
Don't just listen to nature....COPY IT!