Peals of thunder, gently falling rains, the slap of surf against the rocky shores of Acadia National Park, even the roaring of a geyser. These are some of the sounds of nature that have been pulled into musical compositions that revolve around national parks. Produced by Robb Klein, an audio engineer, and Randy Petersen, a musician, these CDs capture the moods of nature found in the parks, and can spur fond memories of your visits while you're far from the parks.

This series, produced by Messieurs Klein and Petersen under the Orange Tree Productions label, captures many of the natural elements that lure us into national parks: Babbling brooks, singing birds, leaves rattled by the breezes, pounding surf, buzzing cicadas, chortling sandhill cranes, bugling elk, bubbling hot springs. These background sounds at times are complemented by human sounds -- on the CD dedicated to Acadia you can catch the tolling of a buoy and the clippity-clop of horses pulling carriages down the paths that wind through the woods of Mount Desert Island.

Against these natural sounds, Mr. Petersen scores compositions that, through the course of the CD's cuts, takes you from morning into night. Piano, guitars, violins, cellos and flutes are among the instruments that accompany nature.

"The idea to record nature sounds actually came from my business partner, Robb Klein. We were both avid back packers and Robb had come across a binaural microphone that recorded in surround sound," explains Mr. Petersen. "We spent a few days hiking around Yosemite and recording to a portable digital recorder. Upon our return we came up with the idea to combine music with the nature sounds to create a kind of 'soundscape.'"

The idea proved to be the easy part. Actually recording the natural background of parks was a bit trickier.

"In terms of production we usually need to make several trips to a park to record. We work mostly early in the morning and late at night in order to avoid any man-made sounds," said Mr. Petersen. "After we return to the studio we spend many hours editing the nature sounds and creating our morning-to-evening time line. Then I go to work writing music that I feel best matches the style of nature. Finally, we mix the two elements together in a studio and create our CD."

For gearheads, the two "use a KU 100 binaural microphone and a portable DAT digital recorder," he said. "We carry a tripod and windscreens as well. As I mentioned, we hike great distances work odd hours in order to avoid human sounds. Many great recordings have been spoiled by planes and other unavoidable sounds. Patience is our best weapon."

The duo has produced more than 30 national park titles, ranging from places such as Acadia, the Grand Canyon, Yosemite, Yellowstone, Carlsbad Caverns and Great Smoky, though they've recorded in more than 50 parks, according to Mr. Petersen.

While the selections at times have a soft jazz, or even bluegrass feel, Mr. Petersen isn't quite sure how to categorize the music.

"Some of it is improvisational and some of it is written out. Most of our fans find it relaxing. Elementary school teachers play it during study time. Spas use it during massage. Many people use it to wind down after a long day. Some of my musicians have a jazz background and some come from a more traditional style," he said. "Making each CD not sound too similar is challenging. As the series grew I tried to write music that was regionally appropriate. So the Blue Ridge music is a little more folk inspired while the Everglades is a little more coastal-influenced."

You can sample the collection at this site. Simply click on the title of choice and you'll open a page that offers several samples from the CD.

Complementing the musical selections is a small collection of 45-50 minute DVDs filmed in the parks, as well as 20-minute-long "postcard DVDs" the two have produced with filmmaker Dennis Burkhart to capture the parks in high definition. "The stories we tell are a mix of history, natural science and human history," Mr. Petersen said. "We also include quite a few activities people enjoy doing at the parks."

And there's also a national parks calendar that displays the photographic talents of Tim Fitzharris, George Huey, Laurence Parent, James Randklev, Mary Liz Austin, Dick Dietrich and others.

Sales also help the national parks, as Orange Tree Productions donates a portion of its income to national park associations and funds. So far the company has been able to contribute $500,000 to various groups that support the parks.