They started off by explaining a little bit about how thatgamecompany developed the game: It all started from the narrative, as co-founder Jenova Chen wanted to try and create a rise and fall story with no actual protagonist to speak of. Then, they loaded up the game itself, and played through most of the levels, talking about their designs as commentary over the gameplay itself.
Both of the developers gave some interesting insight into their respective designs. Diamante talked about how he'd assembled the music for the game, tying it to various flowers and hits in the landscape, layering it down so that as the player opened up new areas, new parts of the soundtrack would not just appear but actually take the lead. First the violin would lead the melody, and then the clarinet would take over, without the violin changing parts.
Johnson spoke at length about how he manufactured the game's sound effects. At each menu screen, he talked about the ambient sound he'd placed in the game and where it came from. The game's first menu screen has a heavy room tone, as it's meant to show claustrophobia and a sense of being trapped, but as the levels progress, the room opens up. The next menu screen plays traffic from Chicago, and then later, a storm playing throughout a city. He talked about how he hid things in the background -- in one menu screen, he'd placed some voicemail messages in very quietly at about eleven minutes in, but he thinks the developers later removed them.
There is one good secret to find, though: after the player finds all of the sets of "secret" blue flowers in each level, a country menu screen appears, and after about ten minutes of just sitting on that screen, you can hear a dog run in on the surround sound, scratch itself, and then run off when it hears another bark in the distance. On that same menu screen, the ambient room tone is actually a recording Johnson had made a few years earlier of the room in which Vincent Van Gogh had died.
Diamante pointed out that most of the music he created for the game is in D major, because it relates "a certain amount of majesty" ("Beethoven calls D major the key of royalty"). Early in the game, the sounds are looped, and eminate directly from the petals, but later on the music progresses up to what he called a "neo-romantic" state -- more dissonant and harsh to mirror the experience and the story. Johnson's effects change as well. Warly on, he recorded lots of movement through grass and wind pitched to various levels, but later in the game, he used more dry grass and eventually hits on water and metal.
The two developers talked about how they intersected as well -- they each had to tweak their own output to match the other. Diamante planned some strong percussion for the final level of the game, but once he realized that Johnson's effects already created a rhythmic booming noise, he tuned his own work up and had it live in a different frequency range instead. And Johnson had to watch his own frequencies as well. The buildings at the end of the game actually make sounds that were originally recorded as Alka Seltzer fizzing under water, and even a few underwater explosion effects.
It was a pretty fascinating panel for a Saturday morning at GDC. Clearly both Diamante and Johnson really enjoyed putting their stamps on Flower, and it was very interesting to hear them talk about the specifics of such an abstract game experience.