Howard Shore's awarded and praised scores for the three Lord of the Rings films are some of the most thematically rich and complex scores in recent times. Shore uses the leitmotif throughout all three scores, which means that characters, places, objects etc all have their own theme or motif associated with them. The themes then change as the characters change. It's a technique that is quite common in film music (Star Wars is another perfect example), but usually not this detailed and complex.
Below is a list, with info and sound clips, of some of the major and/or memorable themes and motifs from the three Lord of the Rings scores. The list is far from complete - there are over 50 themes and motifs in the three scores - and serves only as a basic overview of, and introduction to, the many, many themes found in Howard Shore's wonderful music for these films.
Fore more information about the actual scores, have a look at the reviews of the three available soundtrack CDs.
Character themes
Frodo
Listen to this theme
Represents Frodo, as well as Bilbo and their relationship. Also used to represent home, the Shire and friendship.
This theme appears throughout all of the three scores, and is a central part of Howard Shore's music. Some of the key appearances include the reunion montage in Rivendell, and the breaking of the Fellowship, in the first film, and the end of The Return of the King, where it appears in a more developed form.
Gandalf/The White Rider
Listen to this theme
Associated with Gandalf - The White Rider. Appears in The Two Towers and in The Return of the King when Gandalf rides his white horse, Shadowfax, in great haste.
Aragorn
Listen to this theme
Aragorn's theme is easy to miss, since it's rather short and not that catchy as some of the other themes in Shore's scores. It's basically a repeated, ascending figure, which often is heard together with the Gondor theme in The Return of the King In the first film it appears at Bree, Weathertop and Amon Hen.
The Fellowship
Listen to this theme
In it's finished, fully developed form the theme for the nine members of the Fellowship is a bold, heroic fanfare. It is first heard in full as the Fellowship is formed at Rivendell, but parts of it, and undeveloped versions, appear prior to that. After the death of Boromir, the theme never appear in such a full blown way again, even if short statements - sometimes grand, sometimes not - of it appear throughout The Two Towers and The Return of the King
Eowyn
Listen to this theme
The gentle, and a little sad, theme for Eowyn often accompanies the character's appearances on screen in the two final films.
Faramir
Listen to this theme
Faramir's theme is a subtle ascending melody often performed by pan flutes, and closely connected with Aragorn's.
Arwen
Listen to this theme
The theme for the Elven princess Arwen is easy to miss. Performed by soft choir it appears in The Fellowship of the Ring just before Arwen and Frodo are chased by the Ringwraiths.
Gollum
The Pity Theme
Listen to this theme
Gollum has two themes associated with him - one for each of his personalities. The Pity Themes is used to represent the repressed Smeagol. This theme is most easily identified in the first film, where it appears in full several times - pretty much every time Gollum is mentioned or appears on screen. In the two other films fragments of this theme is used on several occasions.
Secondary/evil scheme theme
Listen to this theme
The other Gollum theme represents the characters more evil, sneaking side. It's based on a cimbalom, playing a descending line of notes, which are closely related to one of the minor Ring themes. Heard in The Two Towers and The Return of the King whenever Gollum is up to something nasty.
The One Ring
Main Ring theme/History of the Ring
Listen to this theme
Like Frodo's theme, the major theme for the One Ring is a central part of the three scores. It is by Shore described as a theme for the history of the Ring and appears over the title screen ("The Lord of the Rings") in all films. Many scenes surrounding, or refering to, the One Ring use this theme in all three films.
Secondary Ring theme
Listen to this theme
A descending 8-note figure, resembling the old Dies Irae melody, played mostly by low strings or brass. Closely related to Gollum's cimbalom theme, this theme seems to represent the power of the One Ring.
Temptation theme/Seduction of the Ring
Listen to this theme
Theme sung by a soft boys' choir whenever someone is tempted to steal the Ring.
Sauron
Listen to this theme
Sauron, and Mordor's, signature is an evil sounding four note motif, performed by dissonant brass. Pretty much all of the scenes involving the Eye of Sauron use this motif and it is often heard when the tower of Barad-Dhur is seen.
The Ring Wraiths
Listen to this theme
The nine ring wraiths' appearances on screen are often underscored with dark choir music, with lyrics in Tolkien's invented Black Speech.
Culture themes
The Shire
Listen to this theme
Upbeat, folksy music, performed by fiddles and tin whistles is used for the problem free life of The Shire. Towards the end of The Return of the King, the tin whistles from the first movie has evolved into a flute, since much has changed, with the hobbits not as "innocent" and shielded from the rest of the world, as they used to be.
Rivendell
Listen to this theme
Soft choir, supported by ascending arpeggio chords, musically represents Elrond's Rivendell.
Isengard
Listen to this theme
The music associated with Saruman's army of Uruk-Hais, and Isengard, with its mines and factories, is a militaristic and brassy descending melody in 5/4 time, with clanging anvils and other unusual percussive effects, such as the sound of chains hitting the strings of a piano.
Lothlorien
Listen to this theme
Represents Galadriel and Lothlorien. In The Fellowship of the Ring, this is the music that opens the prologue, underscoring Galadriels voice over. It is also heard when the Fellowship enters Lothlorien and during parts of the scene with Galadriel's Mirror. In The Two Towers it appears as a militaristic march as the Elves arrive at Helms Deep.
Rohan
Listen to this theme
Howard Shore musically associates the country and people of Rohan with a proud, ascending melody, often performed by the Norwegian Hardanger fiddle.
Gondor
Listen to this theme
The theme for Gondor and Minas Thirith appears in The Fellowship of the Ring, performed by a lonely French horn as Boromir talks about the White City at the council of Elrond. In The Return of the King, this theme has been developed into a stately, brass based, fanfare-sounding melody, heard when Minas Tirith is mentioned or seen. Key moments include the montage when the beacons are lit, where the theme is allowed to really shine.
Other themes
The journey theme
Listen to this theme
Slow theme representing Frodo and Sam's seemingly impossible task and journey.
The nature theme
Listen to this theme
The so called "Nature Theme" is used to represent the constant "battle" between nature and technique, old and new. It's heard in The Fellowship of the Ring when the moth "visits" Gandalf at the top of Orthanc, and in The Two Towers when the Ents attack Isengard.