Singable melodies

As a former singer, I used the humming method most of the time, but there's a few attributes that most vocal lines share:

• Small pitch steps
• Off-beat or syncoped rhythm (depends on style however)
• Ample pauses
• Melodic segments often "bridging" over contrasting harmony
• Ostinato

However, all of this is a matter of style. If it was uniformly enough, we'd had a generator done for this long ago ;-)