Angels do sing, but they are more oriented towards instrumental performance. They like music more than words and melodies. Some angels are closer to God, so they see him more often. All angels have free access to God. Unless there is an emergency, they will not disturb him, because they know how busy is his schedule.
Archangels are the leaders of all the angels.
They have more light, brilliance, compassion, love and divine power than the other angels. Angels live indefinitely, not eternally. After some time period like 200 or 500 years they will take human incarnation or they will be dissolved. Some angels do not want to come down to a manifested form, with a gross human body, so they take incarnation on some other world. When somebody is about to die, we often hear them say that an angel has come.