Import iTunes xml data and convert it into a dataset or table

We can start by importing the file as an XMLObject:

$url = "https://dl.dropboxusercontent.com/u/1012958/iTunes%20Library.xml";

$xml = Import[$url, {"XML", "XMLObject"}];

Short[$xml, 4]

(* XMLObject[Document][
     { XMLObject[Declaration][Version->1.0,Encoding->UTF-8]
     , XMLObject[Doctype][plist,Public->-//Apple Computer//DTD PLIST 1.0//EN,<<1>>}
   , XMLElement[plist,{version->1.0},{<<1>>}], {}, Valid->True ]
*)

The result is the XML document transformed into a Mathematica expression that is amenable to further transformation. Let's define a transformation from the XMLObject into a dataset. The iTunes file (an Apple plist file) is essentially a big nested hierarchy of associations, with the odd list thrown in:

itunesXmlToDataset[xml_] :=
  Block[{XMLElement}
  , XMLElement["plist", _, {c_}] := Dataset @ c 
  ; XMLElement["dict", _, c_] := <| Rule @@@ Partition[c, 2] |> 
  ; XMLElement["array", _, c_] := c
  ; XMLElement["key"|"string"|"data", _, {c_}] := c
  ; XMLElement["integer", _, {c_}] := FromDigits @ c
  ; XMLElement["date", _, {c_}] := DateObject @ c
  ; XMLElement["true", _, {}] := True
  ; XMLElement["false", _, {}] := False
  ; XMLElement[t_, _, {c_, ___}] := (Message[itunesXmlToDataset::ignored, t]; c)
  ; xml[[2]]
  ]

itunesXmlToDataset::ignored = "Ignored unexpected XML element: ``";

This will create the dataset we want:

$dataset = itunesXmlToDataset[$xml]

We can then query, say, for a list of all tracks along with their album and artist:

$dataset["Tracks", All, {"Name", "Album", "Artist"}]

... or perhaps for the playlists along with the number of songs in each:

$dataset[
  "Playlists"
, All
, <| "Name" -> "Name", "Songs" -> "Playlist Items" /* Length |>
]

Had to add the "ReadDTD" -> False option to

$xml = Import[
  "/Volumes/WDC3TBRAID/Downloads/iTunes Music Library.xml", {"XML", 
   "XMLObject"}, "ReadDTD" -> False]

to get WReach's solution to work with Mathematica 11.0. Rest of his solution works fine after that.