Tunes published in 1925 will be entering public domain in 2021

As of January 1, 2021, U.S. copyright will expire for works published in 1925, including the following songs: 

Always (Irving Berlin)

Remember (Irving Berlin)

Dinah (Harry Akst)

Sometimes I'm Happy (Vincent Youmans)

Squeeze Me (Fats Waller) (not to be confused with "Just Squeeze Me" by Duke Ellington)

Sweet Georgia Brown (Ben Bernie, Maceo Pinkard)

Manhattan (Rodgers and Hart - aka "I'll Take Manhattan")

Yes Sir, That's My Baby (Walter Donaldson)

Don't Bring Lulu (Billy Rose, Lew Brown, Ray Henderson)

If You Knew Susie (Buddy DeSylva)

Davenport Blues (Bix Beiderbecke)

Sweet and Lowdown (George and Ira Gershwin)

That Certain Feeling (George and Ira Gershwin)

Bye Bye Blues (Fred Hamm)

Paddlin' Madelin' Home (Harry M. Woods)

This year, the big ones would seem to be Sweet Georgia Brown, Bye Bye Blues, Manhattan, the two Berlin tunes, and the two Gershwin tunes.

In the realm of classical music, Gershwin's "Piano Concerto in F" is losing copyright protection. Other modern classical works entering the public domain are listed on the Wikipedia page 1925 in Music, including pieces by Copland, Elgar, Prokofiev, Respighi, Shostakovitch, Sibelius, Stravinsky, Villa-Lobos, and others.

United States copyright law is quite restrictive as compared to many other countries. According to the provisions of the Copyright Act of 1976 and the Copyright Term Extension Act of 1998 (aka "Mickey Mouse Protection Act"), works published or registered before 1978 remain under copyright for 95 years.

With the passage of the 1998 law, the cutoff date for works entering the public domain became 1922, with any works published in 1923 or later remaining under copyright. Beginning in 2019, however, the clock began running again, with each new year bringing one more year of songs and other works into the public domain. Over the next 20 years or so, most "Golden Age" jazz standards will lose copyright protection.

Many other countries have shorter terms of copyright; one common formula is the life of the author plus fifty years (see this table). For example, in Canada you can record songs written by Wes Montgomery (d. 1968) or John Coltrane (d. 1967), without paying royalties.

Last December I posted an article similar to this one, listing tunes that became public domain in 2020. I'll probably do a yearly update - unless Congress messes with copyright law again, to rescue Mickey Mouse from becoming fair game in 2024.

Notes:

Some internet sources show the copyright date for "Bye Bye Blues" as 1930. Although this is the copyright date shown on the original sheet music, the first recording (by composer Fred Hamm) was released in 1925. According to U.S. copyright law, recordings publicly released can establish the effective copyright date, the same as printed material.

Wikipedia cites 1924 as the year that Harry M. Woods wrote "Paddlin' Madelin' Home." However, this appears to be incorrect. Secondhandsongs.com shows specific dates in 1925 for both publication and for first live performance; the original sheet music also shows 1925.

Cliff Edwards, aka "Ukelele Ike," a popular entertainer in the 1920s, was the one who made "Paddlin' Madelin' Home" into a hit. Edwards had an interesting life in show biz; his Wikipedia bio is worth checking out. Among many other accomplishments, he was the voice of Jiminy Cricket in Disney's "Pinocchio," singing When You Wish Upon a Star. 

Copyright Law of the United States (Wikipedia)