[1][2] All of them should be taken seriously by authors since trade publishing contracts are not covered in the United States by statutory requirements for fairness and may contain vague language, biased terms, and hidden future pitfalls.
Under copyright law, without a written agreement signed by the author, the publisher does not control exclusive rights.
Because the writer has a track record of writing hits, the publisher feels confident that it will recoup its investment.
The advance amount naturally depends on the writer's bargaining power and on the competition in marketplace, if any.
The writer becomes the "co-publisher" (i.e. co-owner) with the music publisher based on an agreed split of the royalties.
In an "admin deal," the songwriter self-publishes and merely licenses songs to the music publisher for a term of years and for an agreed royalty split.
Instead, the music publisher gets 10-20% of the gross royalties received from administering and exploiting the songs for a certain period of time and for a certain territory.
[8] A collection agreement is similar to an admin deal where the writer retains the copyrights, except that the publisher does not perform exploitation functions.
They are like admin or collection deals (with no ownership of the copyrights being transferred to the sub publisher), but limited to one or more countries outside the US.
Often, they are limited to a group of countries, such as European Union (EU), DACH (Germany, Austria, Switzerland), Latin America, etc.