(glabicki) the audience gives to it. you can visualize it as a tree.a seed of it, i bring it until it's about this big, you know, and i present it to the band, and then we work on the foundation of it. then when you perform it, it starts to change all different seasons, and change colors, and then it gets much bigger. then you truly realize that there's something bigger happening. it's not your song anymore. it's gone. [music continues] funding for this program was provided by the annenberg/cpb project. funding for this program is provided by... [ horn honks ] narrator: air pollution -- we can't always see it, but its effects can be deadly. to find ways to reduce its impact, we need to know exactly what pollutants are emitted and how they change as they travel through the atmosphere.