At the beginning of the year, fans learned that Ant-Man composer Christophe Beck was set to compose the score for WandaVision. This seems to have been solidified further with the inclusion of Frozen songwriters Kristen Anderson-Lopez and Robert Lopez as Christophe Beck was also the composer for Frozen, so it's quite the musical reunion.
Up to this point, fans haven't heard anything from the original soundtrack in the series, only popular, but appropriately placed, songs from pop culture. The latest TV spot seems to finally feature a piece of Beck's original composition, which may sound familiar to fans.
A new promo for WandaVision gives fans a small listen of what may be Christophe Beck's original composition for the series, sounding quite heroic and epic.
As for how this may sound familiar, it's likely a modified motif from Avengers suite composed by Alan Silvestri, specifically at 1:06 into the track:
WHAT THIS MEANS
Christophe Beck is no stranger to incorporating motifs from previous composers, as he has done so in his Ant-Man movies when bringing them back for The Falcon from Captain America: The Winter Soldier and The Avengers. The music heard in this latest advertisement from WandaVision seems to likely be a theme for both Wanda and Vision, as they are both Avengers, as exclaimed by Kathryn Hahn's Agatha.
It is entirely more likely that Wanda and Vision will each have their own individual themes independent of one another that more represent their characters. However, this riff on the Avengers would definitely be for the big-scale traditional MCU climax described by Kevin Feige, when Wanda and Vision are fighting together as one, not for the sitcom setting.
It's possible that this music could have been made exclusively for the trailer and might not be part of Christophe Beck's score at all. However, one would imagine that to be a missed opportunity more than anything considering one of the series' theme songs has already been included in its advertising.