The first track on the Fellowship soundtrack is called The Prophecy, and it's 3:55. Wasn't the only music preceding the attack on Mordor just those few notes that plays at the start of every film? There's a slight variation of that in this song, but the one from the movie is not in this song. It might be in one of the other songs though.
The Ride of the Rohirim is 2:08. It starts off with a heavy orchestra that plays a variation of the Rohan theme, with the sharp violin sound as you mentioned. About halfway into the song, it slows down and a flute plays a brief variation of the Rohan theme. Then the song picks up again to what I THINK is the part with the Nazgul.
The Black Gate Opens is 4:01. It builds up into the theme of the Fellowship, then the flute (piccolo?) used in the Hobbit/Shire theme plays a different tune. About halfway into the song, things quiet down and the tempo slows, while the chorus comes in, then accompanied by the flute.
Into the West is one of the best songs ever.