As mentioned earlier, you can learn a lot by copying melodies played by instruments. Jazz singers often improvise in a style known as "scat" where they use syllables instead of lyrics and sing lines inspired by horn players. Soul singer Johnny Adams sometimes imitates a trombone with his voice. Try copying the sound of the trombone in the following example.
This exercise will help you become more familiar with the use of ties. First clap the rhythms while counting the beats out loud. Then try singing the rhythms while tapping your foot on the beat. Make sure you don’t start tapping your foot on the rhythm of the notes instead of evenly on each beat.