Teaser music rundown by Alexander (original forum post):
0:06 – Interesting Empire Strikes Back-like “gloomy” celesta figure.
0:16 – Very A New Hope-like, nostalgic incarnation of the Force theme.
0:23 – The double basses seem to add depth and a little weight to the music – perhaps to accentuate the appearance of the gigantic Star Destroyer?
0:32 – Tender F# on the piano.
0:36 – Beautiful funereal chords orchestrated for low brass, quite perfectly fitting the dramatic imagery and lighting. The major chord at 0:48 came quite unexpected and creates a sense of hope.
0:52 – The return to minor mode, however, resumes the dramatic, funereal mood.
1:01 – The Force theme is continued, again creating a sense of hope and nostalgia.
1:05 – A series of highly dramatic trumpet chords, accentuated by low brass, timpani and percussion and accompanied by high sustained strings and ad lib. harp glissandi set a tense, tragic atmosphere against the battle imagery.
1:18 – Finally releasing all previously built tension, the ‘Yoda and the Force’ fanfare majestically concludes the trailer cue, highlighting the nostalgia implied in Ford’s line, pausing before it and reaching its climax afterwards to emphasize it so as to increase its dramatic impact.
It’s the alternation between the hopeful and the dramatic that makes Williams’s trailer cue so incredibly moving.