Music of Battlestar Galactica (RDM)
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While Battlestar Galactica uses a wide variety of ethnic instruments and styles to create a soundscape that is not usually found in television science fiction, it nonetheless makes use of various leitmotifes for characters, events and places.
Main Title Music
To date, the main titles have been set to two distinct pieces of music. For the first season, a different cue was used in North America than for broadcasts taking place in other regions. The North American cue was a modification of the track "Two Funerals" from "Act of Contrition", followed by a segment played on taiko drums that played over a montage of scenes from the upcoming episode. The "worldwide" cue followed the same structure, but with the funeral cue replaced by a rendition of the Gayatri mantra:
Since the second season, all broadcasts of the show use the "worldwide" version of the main title cue.
Character and event themes
A simple 9-note motif composed by Richard Gibbs for the Miniseries, it is perhaps the most recognizable theme of the series, playing in nearly all scenes with Number Six and used as the "Prologue" of each episode. It is nearly always performed on a Balinese instrument called a gamelan.
Another very common theme, that plays in many scenes with Boomer, especially in Season 2. Initially created as a Helo/Boomer theme for "33" it quickly turned into Boomer's theme. Sometimes played with woodwinds of string orchestra, it is usually performed by gamalans and bells.
Starbuck theme, triumph theme
This theme first appears in a track called "Starbuck on the Red Moon" in "You Can't Go Home Again", in the scene where she leaves the planet in the captured Raider, and in the same episode in "Forgiven" when Adama forgives her for the death of Zak. After that it makes many appearances in scenes with Starbuck, sometimes used a simple fanfare (Home, Part I), or in the background of other tracks, like "Flesh and Bone" or more subtle in the pounding "Prelude to War" in "Resurrection Ship, Part II".
It wasn't initially intended as a theme solely for Starbuck, but since she is the center of many of the show's heroic and triumphant moments, it became associated with her. However, it sometimes appears in scenes involving other characters, most notably Galactica's daring jump into New Caprica's atmosphere in "Exodus, Part II".
Leoben and Starbuck theme, Destiny theme
While their first meeting is in "Flesh and Bone", this theme was composed for their changing relationship in "Occupation" and beyond. It's a small fragment always performed on a Chinese erhu - which is similar to a violin - or zhonghu. It is a representation for Starbuck's anger at being imprisoned, Leoben's love towards her, her self-doubt, fears and the uncertainty about her destiny.
Starting in "33" it can be heard several times in Season 1, but then disappeared for a long time once Helo returned to Galactica. It appears again in "A Measure of Salvation" and "The Woman King". On the Season 1 soundtrack it is included in the form of "Helo Chase".
Adama Family theme
Initially composed for "The Hand of God" it appears twice in this episode. Once as a quiet background piece when Lee talks with his father before the battle ("A Good Lighter") and as a rousing song at the end after the Cylons are defeated ("Wander my Friends").
After that it can be heard in many scenes involving a friendly moment between the two Adamas like Lee visiting his injured father in "Valley of Darkness", Lee being promoted to Pegasus's CO (The Captain's Hand), the two parting before the Battle of New Caprica ("Exodus, Part I"), and Lee receiving his grandfather's law books in "A Day in the Life". It even appears as a general theme for family when Adama decides to "Reunite the Fleet" in "Home, Part I".
An arrangement very similar to the original one at the end of "The Hand of God", but without the vocals, is played during Lee Adama's official send-off into retirement in "Six of One". Instead of Uilleann pipes, Scottish pipes are used to create a more foreign and intimate sound.
The theme reappears in the spin-off series Caprica representing the Adama Family and Joseph Adama specifically. It appears in the pilot episode and again in the episode "There is Another Sky". It is the only theme from Battlestar Galactica to carry over into Caprica.
Apollo also has his own theme first appearing when he destroys the Olympic Carrier in "33". Then in the flashback in "Act of Contrition" at Zak's coffin, and in "The Hand of God" when he improvises his attack plan.
Another distinct occurrence of this theme is in the episode "Six of One", when he visits Kara Thrace in the brig and tells her about his future. It further appears during his confrontation with Romo Lampkin in "Sine Qua Non" when he makes his last argument. 
This started as a very short and simple theme first appearing in "Six Degrees of Separation". In the albums it is included in "Baltar Speaks with Adama" (Season 1) and "Dark Unions" (Season 2). It is quoted in the piano basestar theme from "Torn" and appears in more complex arrangements in "Taking a Break from All Your Worries".
With Baltar's rise to a messianic figure and cult leader (He That Believeth In Me) a new theme is used for him. While evolved from and intertwined with the original theme, it is nearly entirely new, in order to reflect his change and growth. While the old theme represents his dark and sinister side, the new theme stands for his serenity and spirituality. However, the two versions interact and are used as counterpoints in various scenes. The supposedly dark theme used to score spiritual moments and the spiritual theme to score dark moments. Bear notes that his the two sides of Baltar's personality cannot be easily separated. 
This new theme has lyrics sung by Raya Yarbrough. They represent a prayer to Baltar and are heard throughout the episode:
Another version of this theme can be heard in "Six of One" when Baltar sees and talks to a virtual version of himself. This arrangement is a musical palindrome; a cue that reverses itself in the middle and sounds exactly the same being played forward or backward. 
Another mystical theme that replaced the original religious theme. It first appears in "Kobol's Last Gleaming, Part I", during the discovery of the planet; a discovery which is directly linked to Roslin's path. Musically, it is a boy soprano singing in Latin ("All of this has happened before, all of this will happen again. So say we all.").
After that it appears in many scenes featuring Roslin like her in the brig in "Fragged", dying in "Epiphanies", as well as "Lay Down Your Burdens, Part I" and "Exodus, Part I". Its most prominent use though, is in the opening montage of "Occupation" ("A Distant Sadness"), where it is set to new lyrics sung in Armenian, thus making it the only theme in the show to have two sets of lyrics.
A military-sounding brass and choir theme scored for the scene where Tigh declares martial law in "Fragged" and appearing as "Martial Law" on the Season 2 soundtrack. It can also be heard when Sesha Abinell threatens to kill Ellen Tigh in "Sacrifice". The theme appears again in Season 3 on New Caprica ("Occupation", "Precipice"), and when Tigh needs to pull himself together again after the escape from the planet (Hero).
In "Escape Velocity", the theme is reworked to a much more gentler, introspective version. Instead of a clearly western military piece, a duduk and and electric violin are scored in an atonal, middle easter style. 
Roslin and Adama theme
A lyrical and romantic theme, almost a "love theme", that first appears in "Resurrection Ship, Part II" when Adama visits a terminally ill Roslin, and in the second part in the same context. Since then it has appeared in many gentle scenes between the two; sometimes in longer arrangements, but often only as a small introduction. For example when Roslin confesses to rigging the election in "Lay Down Your Burdens, Part I" and later in "Unfinished Business", "A Day in the Life" and "Crossroads, Part II". 
It takes in a more thematic role in "Sine Qua Non" to underscore the moment when Adama realizes that he can't live without Roslin, and when he explains his decision to search for her alone to his son. 
Originally written as a Tyrol/Boomer love theme for "Litmus" it was played on an alto flute there. However McCreary didn't know that it was one of their last scenes together that needed to be scored in that way, and it disappeared afterwards.
Lee and Kara love theme
Adama and Tigh theme
A military theme to underscore the friendship between William Adama and Saul Tigh, usually accompanied by snare drums. It can be heard in many scenes with the two: Adama relieving Tigh of duty in "You Can't Go Home Again", Adama thanking Tigh for saving his life in "Litmus", Adama watching marines restraining Boomer to abort her child in "Epiphanies", and Adama and Tigh talking about Ellen's death in "Hero".
It was first conceived as theme for the military aspects of the Fleet and appears as such when Apollo briefs the Viper pilots in "33". Played on a bansuri at first, it evolved over time. It plays a large role throughout "Sine Qua Non" in Season 4, where it is used for all scenes between Adama and Tigh and when Adama boards the Raptor at the end. 
Minor or guest characters
Usually, guest stars don't receive themes, because they rarely reappear again. For Phelan in "Black Market" however, McCreary created a piano theme. On the soundtrack it appears as "Standing in the Mud". Some of the pianos are played in unusual ways, like striking or plucking the wires directly. 
Daniel Novacek from "Hero" is another guest character with an own theme. The theme itself is a melody carried by duduk, electric sitar and other ethnic strings. Added to that is a relatively complicated string piece, that can be heard throughout the episode. When Novacek arrives on Galactica, when he tells Adama what happened to him, when Starbuck finds out the truth about Novacek and talks with Tigh, and finally his fight with Admiral Adama. Another element to this theme is a short four-chord passage that can be heard when Novacek arrives and again when he departs ("Wayward Soldier"). 
Events and other themes
To kiss or not to kiss
This theme is played at the end of the Miniseries when Dualla and Billy Keikeya, as well as Sharon Valerii and Chief Tyrol are reunited and embrace. In the regular series it appears in "Tigh Me Up, Tigh Me Down" during Billy and Dualla's date on the observation deck, at the beginning of "The Farm" in the scene with Anders and Starbuck, and in "Sacrifice" when Keikeya proposes to Dualla. It can be thus seen as a love theme.
The title is from the Miniseries soundtrack.
Religious ceremony theme
This haunting piece is first in "Act of Contrition" during the funeral scene. When Laura Roslin's religious role became more prominent towards the end of Season 1, it became associated with her (for example in "The Hand of God"), but ultimately a different melody is used for that.
It can also be associated more closely with death as it is also used for Socinus's death in "Valley of Darkness" (originally only a temp track, it was retained) and Admiral Cain's funeral in "Resurrection Ship, Part II". It appears again as both a religious and funeral theme during Cally Tyrol's service for the dead in "Escape Velocity". McCreary says that the track, titled "Lament for Callandra", is his favorite version.
He also notes, while the theme has been used for several occasions due to the producers liking it as a temp track, he always thought of it as the theme for Zak Adama. As such it appears in "He That Believeth In Me" at the end of the discussion between William and Lee Adama about Zak. 
Temple of Five theme
Introduced in "The Eye of Jupiter" when Tyrol walks, like in a trance, over the algae planet and discovers the Temple of Five. It is played by an ensemble of bells, chimes, glass harmonica, glass marimba, tibetian temple bowls and tines.
When Tyrol is inside the temple for the first time, the already established religious theme serves as a starting point for a wordless vocal piece sung by Raya Yarbrough; a melody that previously appeared in "Pegasus" and "Occupation". Added instruments are yialli tanbur, zhong hu and guzheng.
When the star goes nova in "Rapture" it appears with vocals sung in Latin: "All of this has happened before. And all of this will happen again" (from Roslin's theme). When Number Three has her vision more Latin vocals are heard: "Intelligence. A mind that burns like a fire. The hand that lies in the shadows of the light, in the eye of the husband of the eye of the cow". These were previously spoken by the Hybrid in "The Passage".
Not so much as a theme as a rhythm created by taiko drums. At first only used for Centurions, it is prominently used for the ace Raider Scar in the episode of the same name, where it is underscored with a Brazilian berimbau.
Also called "Battlestar Sonatica", it was Ron Moore's idea to underscore the scenes on Cylon basestars with a solo piano piece similar to Beethoven's Moonlight Sonata. McCreary developed an original theme from that point, that serves to bridge the at once familiar, yet alien interior of the basestars, and also represents Baltar's fear.
Final Four theme
According to McCreary, this is an important theme of Season 4 used for the four known Cylons of the Final Five. First appearing in the Season 3 finale for McCreary's arrangement of Bob Dylan’s "All Along the Watchtower", it surfaces fully in "He That Believeth In Me", and can be heard when Tigh pulls the gun on Adama, during the scene with Samuel Anders facing off against the Cylon Raider and later during the secret meetings of the four Cylons.
The soundscape of Battlestar Galactica was originally conceived to eschew the traditional brass orchestra, that it usually associated with science fiction. Thus, one season passed before a string orchestra was used. But since then string orchestras appeared a few times in the series, to great effect. However, they are still used sparingly and reserved for special occasions, to retain their impact.
Named after an italian music form, it makes its first appearances in both parts of "Kobol's Last Gleaming" - in the opening of Part I and as a grander orchestral piece as the end of Part II - and plays during further visits to the Opera House, with which it is usually associated ("Scattered", "Hero").
Another prominent occurrence is the beginning of the "Home, Part II" (on the soundtrack as "Allegro"), accompanying Roslin's team struggling on Kobol, where it ends the whole Kobol story arc that it began. And lastly in the flashback during the climax of "Unfinished Business" (as "Violence and Variations") where it is played in a different tone. 
A Promise to Return
This is a Starbuck/Anders theme whose most prominent use is at the end of "The Farm", where it is performed by the Supernova String Quartet. It also plays when Thrace thinks about Anders in "Scar" and when they meet again in "Lay Down Your Burdens, Part I". After that it appears in several Season 3 episodes.
Prelude to War
Combining aggressive string orchestra with taiko drums, this theme appears at the end of "Pegasus", and before and during the Battle of the Resurrection Ship (Resurrection Ship, Part I & Part II).
Worthy of Survival
This is one of the major non-musical themes in the show. The track was developed out of "Prelude to War" for when Starbuck prepares to assassinate Cain. Then it appears in "Lay Down Your Burdens, Part II", and most prominently when Tigh poisons his wife in "Exodus, Part II", this time in an re-orchestrated version ("Gentle Execution").
It is is played with a sole duduk, violins and violas.
Classic Battlestar Galactica theme
This is of course the main theme of the Original Series, and serves as the Colonial anthem in the Re-imagined Series. It can be heard briefly during the Viper flyby during the decommissioning ceremony in the Miniseries and as the conclusion to D'anna Biers's documentary in "Final Cut".
McCreary worked with Original Series composer Stu Phillips to recreate the theme as closely as possible, but also offers a variation of it played with ethnic instruments at the beginning of the track.
Music not original to Battlestar Galactica
This piano piece by Philip Glass plays in Kara Thrace's Delphi apartment in "Valley of Darkness". She says it was played by her father. It is heard again briefly with Tigh at Adama's beside. In reality, it is Bear McCreary at the piano.
All Along the Watchtower
This is a newly arranged version of Bob Dylan's "All Along the Watchtower", used in the Season 3 finale "Crossroads, Part II" and hinted at earlier in "Part I". It is sung by Brendan McCreary (aka Bt4) and features Oingo Boingo's Steve Bartek playing guitar. Bear McCreary changed some of the instruments using an electric sitar and an Indian harmonium.