Where to Find Free Sheet Music Online Legally
What Kind of Sheet Music Do You Want to Find?
I Want This Sheet Music, Where Can I Find It?
This is a very common question, particularly on the internet. The music concerned falls into one of two categories: either the work is in the public domain, or it is not. The answer to this question of finding the piece largely depends on whether the music you are looking for is in the public domain. However, this is in itself a complex question, and so a little bit of background information is necessary.
In general, a work composed before January 1st, 1923 is in the public domain. The exception to this is certain composers, who are covered in the case Golan v. Holder. Therefore, if a work was published in a country without a copyright agreement with the United States prior to May, 1973, it is likely that it is no longer in the public domain. In addition, certain works whose copyright was not renewed in the United States, but which were in copyright in the composer's country will be restored to copyright status.
Works first published in 1923 will enter the public domain on January 1st, 2019.
To find the sheet music (including transcriptions), for a good deal of works in the public domain, visit the International Music Score Library Project.
I Want a Free Score to a Modern Piece of Music!
Unless the composer of the piece has explicitly released the work into the public domain (which is highly unlikely), their work is protected by copyright. That means that obtaining the music without payment is illegal.
To get a copy of unpublished pieces, you can usually contact the composer of the work through their official web site. For composers who have died, usually the heirs or legal representatives can be contacted through the composer's official web site, and permission is sometimes granted for a fee. For work that has been published, you will have to pay for a copy of the music. The few dollars it will cost to buy the sheet music is not worth risking a lawsuit over copyright infringement.
Unfortunately, not as complete as the author would like you to believe, but this book is a good starting point.
What About a Recording?
If you are looking for a sound recording, that is where copyright law gets really complicated! Sound recordings made before February 15, 1972, are protected under state law, rather than under federal law, and so to find out if a recording is in the public domain, you will have to find out in which state it is protected and look up the copyright status of the work. In some cases, the artists have explicitly released works into the public domain, and if you can find verification of that official release, you may do whatever you wish with the recording. The number of recordings meeting that qualification is extremely small. Therefore the earliest that the recordings will enter the public domain, in general, is on February 15th, 2067.
Some recordings have been released under a Creative Commons license, especially on the Internet Archive. With those recordings, you may use them as long as you follow the rules of the particular Creative Commons license (not all of those Creative Commons licenses are equal, so be sure you understand the details of each license).
For sound recordings made after the February 15, 1972 date, the term of copyright is the life of the author plus 70 years. (Note that there are actually two or more copyrights: the performer and the audio engineer, and there may, in the case of certain works, be a corporate copyright owner as well.)
How Will I Ever Sort This Out?
Really, you can't sort through most of this by yourself. It takes a lawyer to comb through all the applicable copyright law. However, there is some help available at the the Cornell University Public Domain Resources page.
In general, there are three major sources online where you can look for public-domain music: the aforementioned International Music Score Library Project, the Internet Archive, and Wikipedia. If the music is not available on one of these web sites, it is probable that you will have to pay for it to acquire it legally.
Again, the few dollars you might save by acquiring a work illegally will be offset by many thousands of times if the artist decides to make an example of you. Especially if you are planning on performing the music in a public place, someone could easily upload a video of you playing the work illegally to the internet, and you will have absolutely no defense.
Also be aware that even if you own a copy of the sheet music of something still under copyright, that does not give you the right to perform the music publicly. You can either license the music from the composer, or you can secure permission to perform the work. In many cases, that permission will be restricted to a specific time, place and date. Any deviation from any of those conditions (such as a rain date or venue not specified) will be in violation of that permission and you may be sued.
But I Want to Perform Some Modern Music!
All may not be lost. If you live in the United States, it is commonly the venue owner who must provide the license. How can you tell if the venue owner has a license to allow performers to use modern music? The simplest way is to look for the BMI and ASCAP stickers on the front door. Whether you play for fun, or for pay, get the owner of the venue to sign a contract and have the contract make clear that the owner is liable for ensuring that the rights have been secured.
I am not a lawyer. Please consult an intellectual property lawyer for any specific advice. I will not be liable for any actions undertaken without the advice of a lawyer who specializes in intellectual property.