ll <- readLines(textConnection("ÁÀDFDS (artist 1)
  1 Lorem ipsum dolor sit amet, consectetur adipiscing elit.
AB (artist 2)
2 Nulla sollicitudin elit in purus egestas, in placerat velit iaculis.
  BBDDED (artist 3)
  az*ù*ù*ù (bad string)
  3 Nunc et eros eget turpis sollicitudin mollis id et mi.
      4 Mauris condimentum velit eu consequat feugiat.
   5 Suspendisse sit amet metus vitae est eleifend tincidunt.
  ÉÈDFSF (artist 4)
6 Sed cursus augue in tempus scelerisque.
...gdgdgdg (bad string)
7 in commodo enim in laoreet gravida."))
ll <- gsub("^[\\P{L}\\D]*?([\\p{L}\\d])", "\\1", ll, perl=T)
ll[grep("^\\W*\\d+\\s|\\p{Lu}['\\p{Lu}]", ll, perl=T)]