Long before radios, movies, television and the Internet popularized music, sheet music made compositions of the good old days popular, or at least, known.
Defined, sheet music is a printed musical composition. Musicians back then publish their songs in these unbound sheets of paper. Performers also used these as they played a musical piece to an audience.
Today, sheet music is still made. However, it is used mainly by musicians such as singers, pianists and guitarists. For many, they are just mere sheets of paper. You will often find old sheet music hidden in piano benches or placed in a box, untouched for ages, collecting dust.
If you are interested in finding old sheet music, you can still see many of them in music stores. You can even find them in several web sites that offer them in computer-readable and easy to download formats. There are sites that sell sheet music for as low as $3 to as much as $50. There are also sites that allow sharing, downloading and printing of sheet music for free.
Most free sheet music available is sheet music of classical and old songs. This is because the copyrights these old songs and classical music have already expired. In the US, a copyright expires 70 years after the death of the last surviving creator of the music. Furthermore, the law states that those published before 1923 must be in public domain.
There are sites that offer musical scores of popular and latest songs (scores are printed music of all instruments used to play a piece). Usually, the free downloadable and printable sheet music available are only samples and are merely parts of the entire score.
New arrangements and editions of the old songs may have been made. Some of these new versions are freely available while some are sold for a reasonable price. There are also personal sites of music enthusiasts that offer free sheet music of their favorite songs. You can check these sites to look for sheet music of the songs you like.