If you're a "Children of Earth" fan, you'll undoubtedly recognize specific visual moments from a scene when you hear the track from it. The 40 tracks are arranged chronologically by Day to remind you where the music added an important layer of meaning to the on-screen action.
I've listened to this soundtrack a lot in the past few weeks, and I'm continually impressed with the variety of ways in which character themes blend beautifully with the drama shown on screen. As well, if you're familiar with the character themes for Tosh, Owen, Jack, and Gwen (from the previous Torchwood CD--also a fantastic soundtrack), you'll find them added to important moments within new music. For example, listen to Jack's departure song, "I Can Run Forever," and you'll also hear some of Ianto's and Tosh's themes (accompanying the scene where Jack mentions those he leaves behind). Within a "danger" track like "Judgment Day," you'll hear a bit of Jack's theme.
The lushly emotional cuts are nicely offset by the danger music that also pulses through the CD. The soundtrack balances faster-paced action tracks with reflective moments; it nicely summarizes all the many experiences and emotions of "CoE."
One of the strengths of the Torchwood soundtracks is specific music relating to key characters, and the poignant additions to the "CoE" soundtrack are "Ianto's Theme" and the longer, crescendo-ing "The Ballad of Ianto Jones." Each character's personality is captured by his/her theme. It's worth going through both this and the previous soundtrack to listen just to those character moments, because they appropriately capture the essence of the characters we've come to love.