I have listened to this recording multiple times from multiple sources in addition to the actual show.
In the Game of Thrones soundtrack, Main Title at 0:08, a cello (or other low range stringed instrument) begins playing. From what I can hear, there is a buzzing sound in addition to the note the instrument is playing. As the rest of the orchestra plays their parts, this buzzing sound seems to be drown out. However, it is again apparent, though fainter, around 1:34.
Is this the result of a deliberate technique designed to give the music a rougher texture or is this a flaw in the instrument, bow, or performer?