You should check when the performance took place: if it took place in Australia before 1 October 1989, you do not need to consider the issue of performers’ rights. However, if the performance took place after this date, you will need to check whether or not the performers consented to being filmed.
You may also need to get permission from whoever owns copyright in the music and in the footage you want to use.
Outside performers’ rights, there is no general law in Australia preventing people being filmed without their permission. There are, however, limited privacy laws and laws which affect certain uses of a person’s image which might be applicable.
There’s an exception in the Copyright Act for the “incidental” inclusion of an artistic work in a film or broadcast, but there is no similar exception for the inclusion of music.
If, for example, you are shooting footage of a street and you capture on the soundtrack either people singing or playing music or music from a TV, radio or CD player, you will generally need permission from the relevant copyright owners (usually the music publishers and the relevant record company if the music is from a recording). You will usually need this permission whether or not you are filming the source of the music.
If people are performing the music, you will also need to consider the rights of the performers. (Usually, you need consent to record them).
You may need a copyright clearance if your film is based on someone else's account of those incidents (for example, in a book). You are likely to need a copyright clearance if:
that account is protected by copyright, and
the copyright has not expired, and
your film uses a "substantial part" of that account.
Legal obligations other than copyright might also apply. These could include legal obligations relating to misrepresentation of facts (such as defamation), and legal obligations relating to confidential information.
You are likely to need permission unless:
copyright has expired, or
a special exception applies.
One special exception, under Australian law, allows the inclusion of an artistic work in a film if it is “incidental".
Note there are differences in the copyright laws of other countries which can mean that a clearance is needed for another country even if it is not needed for Australia.
Note also your obligations regarding the moral rights of artists whose work you include in your film.
There are no special rules that allow video artists or film makers to use material merely because it is posted to Youtube or any other site.
In some cases, people posting to YouTube enable features such as “embed” and “download”, but these of themselves would not give you permission to use something from the site in a new video work.
In some cases, however, one of the fair dealing exceptions may be available to you (for example, if you are using the material for parody or satire), but each case will depend on its own facts.
If an exception is not available to you, you will need permission. Given the risk that the person who uploaded the material to YouTube may not own any or all of the relevant copyrights (for example, music and recordings on the soundtrack may be owned by music publishers and record companies), make sure you list each of the relevant copyrights you want to use, and get appropriate warranties and indemnities from anyone purporting to be able to give you permission.
Make sure you consider each of the relevant pieces of copyright material when considering whether or not you can rely on an exception.