These are the required copyright attributions on my arrangement of 3 pieces by Astor Piazzolla,
I'm not a lawyer, and I don't play one on TV...
I've used up a lot of brain cells over the last 3+ decades getting my head wrapped around the copyright law. It's overly complicated (IMO) and a constantly moving target.
Some basic guidelines - not legal advice and this only applies to the United States:
Works copyrighted prior to 1923 are in the public domain - look for the original copyright date.
Works copyrighted between 1923 and 1963 (copyright not renewed) are in the public domain.
Works copyrighted between 1923 and 1963 (copyright renewed) will be in the public domain 95 years from the original publication date.
Just because there is no renewal date on your copy of the source material or the copy that you checked out of the library does not list a renewal date does not mean that the copyright was not renewed.
Works copyrighted between 1964 and 1977 (no renewal required) will be in the public domain 95 years from the original publication date
Works copyrighted since 1978 will be in the public domain 70 years after the death of the composer/arranger/orchestrator.
As I tell my kids, being good and not getting caught are not the same thing.
Some rudimentary observations - this is not legal advice:
In the United States (and that is an important distinction), typically anything with an original copyright date of 1923 and before is probably in the public domain (PD).
When arranging something with an original copyright date after that, it's best to do the research (see below for a start).
Just because something is public domain in the US does not mean it is PD in other countries - and vice versa.
In my experience, a license to arrange and publish a work can be expensive. For example, I paid $1800 to secure a license for my arrangement of An American in Paris.
A copyright owner is under no obligation to grant a license to arrange. They may also limit the use to "personal use only - not for distribution."
Side note: I have a few white whales in this category - works I've been trying for years to get permission to arrange. I currently have 5 requests out and pending license.
Until the copyright owner has given permission for a work to be recorded, the copyright owner owns the first right to record.
Once the copyright owner has granted permission for a first recording, permission for anyone else to record their own version of that piece is compulsory. You'll have to seek out a mechanical license and pay the owner a few cents for every copy of the recording distributed - not just sold.
One of the oddest aspects of the copyright law: that compulsory permission also includes making an arrangement, but ONLY for the purpose of recording your own version.
Purchasing a piece of music does not grant the implicit permission to do anything with it (no photocopies, no recording, no arranging, not even public performance though that is the most often overlooked).
Orchestras and other ensembles routinely lend purchased music to others - if that music is not in the public domain, that is a violation of copyright law.
You may be thinking how can libraries then lend out copyrighted material? The loan of that material is not technically distribution and has a differently intended purpose. In other words, an orchestra or band library is NOT a lending library. If you are borrowing something with the intended purpose of public distribution through performance, you are circumventing the basic purpose of the copyright law. That purpose is to grant control of distribution methods of intellectual property to the rightful owner.
Reproduction (photocopies or scans) of the original plates of Brahms 2nd Symphony - okay. Bernstein Candide Overture - bad juju.
Fair use is really misunderstood, especially by those in academia for whom it was primarily designed. Just because one works in a public institution with education listed as one of the charitable purposes does not grant rights to photocopy anything. There is a rule which allows VERY limited reproduction for purely educational purposes - it's something like 10% of the original material (a tuba part is not 10% of the original material because the part standing alone is copyright protected - 10% of the part may be allowed).
When an arranger or orchestrator (or editor) makes a new version of a public domain work, that new version is copyright protected. The arranger or whoever the arranger transfers copyright to, owns the copyright as if it were a new work. This also means that an arrangement or orchestration cannot be recorded first without the permission of the new copyright holder (even for archive purposes).
The same is true of editions - scholarly editions can be copyrighted (hence the business model of Urtext). When arranging or orchestrating, make certain the source material has not been recently edited and newly copyrighted.
Copyright is created the moment original musical thought (yes, this includes arrangements and orchestrations) is fixed in a tangible medium.
It's a good precaution, but it's not necessary to register a copyright.
Mailing yourself a copy of your own work to establish copyright is not really useful.
To establish bullet proof copyright of an arrangement, transcription, orchestration or edition, a work must be something beyond the scope of what a mere technician could achieve. For example, Bach Chorales in open score format for brass quartet without editing will not hold up in court as a valid copyright, even if the clefs, key, and/or register were changed - to establish copyright, one must bring more to the table than that.
Arranging another arranger's copyrighted arrangement or orchestration is a copyright violation (see above).
Side note: - on a few occasions, I have heard an arrangement and thought that it was a really great idea, but it was written so poorly that the concept died on the vine.
I have used other arrangements as a rudimentary template for writing my own copyrightable version.
Which brings me full circle to the final concept:
An idea cannot be copyrighted, trademarked, or patented. Only the unique expression of that idea can be protected.
"Top of the Muffin to you!" (extra credit for correct attribution).
Did I mention? I'm not a lawyer and this is not legal advice.