Copyright is a number of different rights which the law grants exclusively to owners of copyright works.
If you are a composer of original music or a songwriter of lyrics, the Australian Copyright Act (1968) gives you the right to:
As the copyright owner of your original music and lyrics, these are your exclusive rights.
Nobody else can use your work in these ways without getting your permission first, and, where applicable, paying you a royalty for this use.
The length of time that a work remains in copyright including the period after the copyright owner has died. In Australia, copyright on a musical work continues for 70 years from the creator's death. In New Zealand, it continues for 50 years after death. It varies in other countries.
Please note that the policy on copyright law is different in every territory. Please check your local laws as necessary.