I asked the singer of a song I am using, and he agreed to me using his music, provided I credit him. Do I need anything else, such as an agreement or signature?
First and foremost, I am not a lawyer. You should always consult a lawyer in regards to legal questions - the legal system is often very fickle, and often changes dramatically from location to location.
Can you legally use this music piece? It is impossible to tell.
You tell us you have permission from the singer. The first thing you need to find out is whether the singer actually holds all copyright reservations for the piece. The singer performing in the piece does not necessarily mean anything, in regards to copyright. Do your research. Find out who actually wrote the piece. Find out if it is a solo work, or a collaboration. Find out if the original writers actually own the copyright; under certain circumstances, the actual copyright could still belong to somebody entirely differant.
Do not assume that any one person retains all copyright on the simple basis that they are the one performing the piece. It is also worth considering that you could still be receiving the wrong information from the artist; perhaps they do not realise that the ten second sample they took from another song could impose serious copyright infringement. Perhaps they know very well, but would rather just say they hold all rights, to ensure further publicity.
What should I do to legally acquire use of a song?
The only effective way to legally acquire the use of a song is to consult a lawyer. Preferably a copyright lawyer, as they will be more knowledgeable of the particular domain of law you are trying to follow. I say effective, because there is no sure-fire way to ensure legal process; at least, not in regards to ensuring you do not get sued. The potential copyright holder could still sue you after all assurances have been made. It is then up to the courts to decide whether you have legitimate ground; in the mean time, you could be up for very expensive legal fees.
On receiving confirmation for use
You also want to consider the form of your original "contract". How has the artist approved usage of their song? Via electric message? You would have to prove that you were actually talking to the artist; and not somebody else. It does not matter who that "somebody else" could be - a friend, a family member or somebody hacking in to the account - this assurance could easily be thrown out on the chance that it was not the original artist replying to your messages.
If this "contract" was verbal, you're in even more trouble. In many cases, a verbal contract is referred to as "non-binding". It is not that they have no merit, but it is often hard to prove that they actually said what you claim they said. It becomes a case of "he said, she said", which again, often offers no bearing in court.
On writing up a written contract
Do not bother signing a legal contract, yourself, without a lawyer. In some cases, a contract is null and void simply on the basis that the parties signed without a lawyer.
TL;DR: If you want to legitimately use somebody else's song in your game, you should consult a lawyer. If you can not afford to consult a lawyer, you can not afford to defend your right to use the song, should any issues actually come about.
The singer is just a small part of a music track. It consists of:
- The vocals provided by the singer
- The text of the lyrics
- The composition of the melody
- The arrangement of the melody
- The performance of musicians playing the melody
- Individual audio samples used in the song
- The final audio mix of all these things together
All these creative inputs can be provided by different people and when any of these people feels that their copyrights are violated by you they might cause you trouble. So you need to make sure that you own the rights to all of this before you use a song in your game.
To make things simpler, most record labels secure the exclusive and redistributable rights to all these things before they publish a song, making it possible for them to relicense the whole song as a whole.
A common clause for art license contracts is that the licensor guarantees that they own all the copyrights and that they are liable in case that turns out to be wrong. You might want to ask a lawyer specialized in copyright law to draft the contract.
In the 90s I worked for the largest computing magazine in Hungary and we had a cover CD, some 30 000 copies a month. We offered up and coming musicians to put their music there for free. This was insanely popular with our audience and the musicians both. A bit later the collective rights management agency in the country sued us and won because the law said you needed to pay them a fee per copy per minute. This is called a mechanical royalty. So even if the copyright holder grants you a license and very glad actually to spread their music you might not be in the clear. Definitely lawyer up.
Licensing from the authors
This can be complicated if a copyright collecting agency or a licensing agency in involved. If you deal directly with the authors, they can issue you a license.
If that license is exclusive, we want to make sure it is not fake, thus we want the license written and signed by the author or digital and digitally signed. The author may want to seek legal advice to do this.
Authors, because - as the other answers have stated - the audio recording involves diverse intellectual property, including the interpretation of the lyrics and melody, samples, audio composition, etc.
You have permission from the singer of the music you want, is the singer also the writer of the song? What about the people who play instruments? Did they use any samples from third party? In addition, somebody composed and edited the final recording, what about that intellectual property?
This can be further complicated. For example, if I want to record a song that written by another musician, I need to license that song, and the license I acquire may or may not allow me to license my recordings of it.
Licensing from a licensing agency
You must find out if a licensing agency manages the particular work, in accordance to depending on local law.
In some places, the law states that authors needs an affiliation to a licensing agency appointed by the government in order to legally earn revenue form their work, this is not true worldwide. Furthermore, in some countries, the author needs to apply for a special permit to license their work outside of a licensing agency.
If there is a licensing agency managing the copyright of the work, that agency will define the procedure to follow to license the work, and how to pay any loyalties.
Licensing agencies should make it easy for authors to license their work and earn loyalties from them. They serve as intermediary between the licensee and the author, and often charge a fraction of the loyalties (although there are other business models and payment schemes for the authors, those are particular of the agency in question).
Consider, for example, a T.V. show that used music from a particular artist. Evidently, the T.V. producer has to acquire a license for that music. Furthermore, according to that license, reruns of the T.V. show may generate loyalties for the author. A licensing agency will keep track of that, and keep the revenue stream flowing... for a fee.