EVOLUTION IS THE GREATEST composer-just stand on a lonely beach, and you'll hear. From the wind and waves, from the voices of gulls, nature conducts a symphony grander and more pleasing than any played in a concert hall. And the concert does not end at the seashore. Over all the earth's surface there may be 10 million unique sounds produced by birds, amphibians, mammals and insects. Yet despite their pull on our psyche, only about 1 percent of these natural rhapsodies has been properly recorded and archived. Far fewer have been systematically studied. With a little care, you can capture sounds never before recorded and study their patterns.

You might even be able to contribute them to a growing national registry. The Library of Natural Sounds at the Cornell Laboratory of Ornithology holds the world's largest collection of nature's voices. The archive contains songs from more than half of all bird species, not to mention insect chirps, amphibian croaks and mammal bleats. Contributing to this library of course demands high-performance devices, which can run into the thousands of dollars. Fortunately, discoveries can come more cheaply. With the help of some special software, you can do original research with a modest recording system.

learn how to recognize animals by their calls. Read field guides, talk to naturalists and, most important, listen to recordings. The best resource for studying natural sounds is the Cornell library, but it charges a minimum of $22.50 for sounds. Fortunately, many collections of natural sounds are now compiled on CD. The Guide to Bird Sounds is the National Geographic Society's audio companion to its printed field guide, and the Peterson Field Guides offer calls from nearly every North American bird. If you have a CD-ROM player, check out Bird Song Master, which uses your computer to help you learn to identify birdcalls. Frog fans might try Voices of the Night, produced by the Cornell lab, which eavesdropped on lovesick amphibians. All these products can be purchased from the Library of Natural Sounds and other specialty retail outlets.

Recording nature successfully demands that you be able to isolate one particular sound and screen out all the rest. A parabolic dish does this task quite well. With a microphone at its focus, it will collect only sounds that fall parallel to its center. The dish, however, must be small enough to be carried easily in the field, limiting its diameter to about one meter. To be reflected, a sound wave must fit inside the dish. Unfortunately, that means it will not amplify a sound wave longer than one meter. So the lowest pitch this dish will amplify is 344 hertz-roughly F above middle C. Luckily, most animals produce sounds above 344 hertz; for instance, birdcalls characteristically range from 2,000 to 6,000 hertz.

Parabolic reflectors are not hard to come by. Edmund Scientific (telephone: 609-547-8880) carries an 18-inch-diameter, polished-aluminum reflector (No. 80254) for about $35. Radio dishes are also parabolic; a military surplus shop may have a few of the right size. And remember, any dish approximately parabolic will provide some amplification and directionality-some woks and large salad bowls work surprisingly well. You can also experiment with tightly stretched umbrellas, plastic snow-slides, decorative housings for light fixtures and even the bottom of a barbecue grill.

Once you have a parabolic amplifier, you will need a microphone, a tape recorder and a set of headphones. Drill a hole at the base of the parabolic dish large enough to accommodate the microphone wire. A stiff metal-wire coat hanger makes a good support for the microphone. Coil up one end of the hanger wire at the base of the dish and bolt a metal plate on top of the coiled area to hold the wire to the dish [see illustration below]. With duct tape, secure the free end of the hanger wire to the microphone, which should face the dish You will have to experiment to find the best position for the microphone. The wire from the microphone can be hooked directly to a portable cassette recorder. The electronic equipment does not have to be fancy-you can learn a lot by stalking around with a $30 microphone and $50 tape machine.

To gain real-world recording experience, practice at a zoo. Here animal sounds are plentiful and confined to small areas, and it is easy to recover from equipment mishaps. When in the wild, be aware of what is happening behind your target. Like a telephoto lens, a parabolic microphone will compress the distance between foreground and background. Noises coming from behind your target will sound louder on the recording than they did to your ear. So position yourself to aim either upward or downward at your target. Then your background will be only the quiet sky or ground.

A few years ago only professionals could dissect sounds. Today you just need a little software. Canary, a Macintosh program designed at the Cornell ornithology lab, is ideal for studying natural voices. It lets you instantly see how any tone is constructed [see illustration at right]. Canary lets you zero in on any part of the melody and analyze it in detail. The program also helps to hide sins committed in the field: unwanted sounds, like distant rumblings from a truck, can be deleted. But it is Canary's ability to compare different sounds that makes it so powerful. Canary tests sounds mathematically to see how alike they are. For identical sounds, the result is 1; for completely different ones, the result is 0. The program shifts one melody past the other in time and compares them. Then it plots these numbers so you can observe the difference graphically.

This feature makes all kinds of explorations possible. You can measure the difference between two consecutive calls from the same bird, compare one bird's song with that of another from 5 the same species and test your ideas about the notes from closely related species. With a bit of cleverness, you can measure the time delay between when -the sound arrives at each of three widely separated microphones and hence locate the bird's position when it called. (Sound travels about 344 meters per second and arrives first at the microphone closest to the animal.) You could piece together an individual bird's movements and determine the boundaries of its territory. Or try mapping the search pattern of a hunting bat by its sonar- the possibilities are endless. Given its power, Canary is a bargain at $250.

If a Windows or DOS machine lives on your desk, consider Wave for Windows (Turtle Beach, $149), Sound Forge (Sonic Foundry, $495) or Software Audio Workshop (Innovative Quality Software, $599). The drawback is that these programs were designed for sound engineers, not scientists, so they lack some of Canary's most useful features. I tip my hat to Wave. It has all the power necessary to view sound and decode its frequencies. Although musicians may enjoy the features of Wave's more expensive competitors, scientists will not see much difference. All these packages should be available from large software catalogues.

If you have your heart set on contributing original data to the Library of Natural Sounds, you will need professional equipment. But a good microphone could set you back $1,000, and high-quality tape recorders run upward of $2,000. So what is an amateur to do? One way is to find other people interested in recording natural sounds and pool your resources. Contact local nature organizations or post a message on an electronic bulletin board on the Internet-try the swap-meet site on the Web page of the Society for Amateur Scientists. And don't forget sound studios and local colleges; there may well be nature buffs already lurking among the equipment you need. If you are really ambitious, form a nonprofit corporation, which is eligible to receive tax-deductible donations (get a copy of 172e Nonprofit Corporation Handbook, Nolo Press, 1995). Audio manufacturers and supply houses are sometimes happy to donate outdated but perfectly functional equipment.

For more information about recording natural sounds, contact the Library of Natural Sounds and request the free equipment sheet, which describes what you will need to get serious about this hobby. Reach them at Cornell Laboratory of Ornithology, 159 Sapsucker Woods Road, Ithaca, NY 14850; e-mail: libnatsounds@cornell.edu or http://www.Ornith.cornell.edu/birdlab.html; telephone: (607) 254-2404. To learn more about software and novel experiments you can do, send $2 to the Society for Amateur Scientists, 4951 D Clairemont Square, Suite 179, San Diego, CA 92117, or download the information free from http://www.sas.org/ or from Scientific American's area on America Online. Some sample birdsongs are posted on the Scientific American area and on the Cornell Web page.

The Society for Amateur Scientists (SAS) is a nonprofit research and educational organization dedicated to helping people enrich their lives by following their passion to take part in scientific adventures of all kinds.