How to display list of items (grouped alphabetically) using UICollectionView List API?

I'm trying to display a list of songs using UICollectionView's List API. I would also like them grouped by the first letter of the song. At first, I thought I'd have something like this:

let sections = [
    LibrarySection(name: A, songs: [
        Song(name: "A Song"),
        Song(name: "Another Song"),
    ]),
    LibrarySection(name: B, songs: [
        Song(name: "B Song"),
        Song(name: "B another Song"),
    ]),
]

var snapshot = NSDiffableDataSourceSnapshot<LibrarySection, LibraryRow>()
snapshot.appendSections(sections)
sections.forEach { section in
    snapshot.appendItems(section.songs, toSection: section)
}
dataSource.apply(snapshot, animatingDifferences: true)

But I facepalmed when I realized the smart thing to do is this:

let items = [
    Song(name: "A Song"),
    Song(name: "Another Song"),
    Song(name: "B Song"),
    Song(name: "B another Song")
]

The question I have is, what would the snapshot logic look like such that I am minimizing the amount of times I have to instantiate items and sections?

var snapshot = NSDiffableDataSourceSnapshot<LibrarySection, LibraryRow>()
???
dataSource.apply(snapshot, animatingDifferences: true)

Thanks for any feedback you may have!!!