This is the 218th most frequent Slovenian word.
nekatere
"Some" or "certain."
Here, 'nekatere' functions as an adjective meaning 'some' to specify an indefinite subset of books.
Nekatere knjige so na mizi.
Some books are on the table.
In this sentence, 'nekatere' serves as a pronoun referring to an unspecified group of people.
Nekatere ne verjamejo, da je to res.
Some do not believe that this is true.
'Nekatere' is again functioning as a pronoun selecting an unspecified subset from a defined group (the songs).