Use your own original music.
Not unless you make a recording of it and publish it without permission of the copyright owner, assuming the music is copyrighted.
copyright of music belongs to the sound recording company, composer and lyrics writer if the music is quite old (mozart etc) you can publish it, otherwise it is a copyright infringement to publish music on youtube without the owners permission The best way to avoid copyright infringement on YouTube is to post only content that is entirely your original work.
It is not legal. If you do not own rights to the music it is copyright infringement.
buy cd's
With a license, yes. Without a license, no.
Without a license, yes.
The owner of a copyright in music has the exclusive right to perform the work
No, copyrighted music cannot be used in your movie without permission, especially if it is to be published. You should always get permission from the respective copyright owners if you want to use content you do not own.
Unless the performance would fall under the "fair use" or other exception to copyright law, yes it is illegal to perform copyrighted music without permission.One of the rights that copyright confers is "the right to perform the work publicly".
This is a very contentious issue and depends on the country the music is stored in, the country it is being downloaded in, the relationship the site has with the copyright owners and whether or not a copyright even exists on the music. In many countries it is illegal to host and download copyrighted music to/from the internet without permission from the copyright owner. With permission, a site may be allowed to do so. Napster's original incarnation was shut down for making music downloadable for free without permission from the copyright owners. One way around copyright laws is by downloading music that has been released into the public domain under licenses such as the Creative Commons attribution-non commercial share-alike license which allows the music to be freely copied and manipulated so long as the original author is credited and that it is distributed under the same license.
The music industry relies on copyright protection to sustain itself.
Without permission, yes it would be an infringement of the artists right to control distribution of his/her music.