The light went on again; the view vanished.

Dr. Cray said, "Do you know what we're doing in there?"

"You're recording brain waves? Just a guess."

"A good guess. We are. It's a laser recording. Do you know how that works?"

"My stuff's been recorded by laser," said Bishop, crossing one leg over the other, "but that doesn't mean I know how it works. It's the engineers who know the details…Look, Doc, if you have an idea I'm a laser engineer, I'm not."

"No, I know you're not," said Dr. Cray hurriedly. "You're here for something else…Let me explain it to you. We can alter a laser beam very delicately; much more rapidly and much more precisely than we can alter an electric current, or even a beam of electrons. That means that a very complex wave can be recorded in far greater detail than has ever been imagined before. We can make a tracing with a microscopically narrow laser beam and get a wave we can study under a microscope and get accurate detail invisible to the naked eye and unobtainable in any other fashion."

Bishop said,,.It that's what you want to consult me about, then all I can say is that it doesn't pay to get all that detail. You can only hear so much. It you sharpen a laser recording past a certain amount, you bring up the expense but you don't bring up the effect. In fact, some people say you get some kind of buzz that begins to drown out the music. I don't hear it myself, but I tell you that if you want the best, you don't narrow the laser beam all the way…Of course, maybe it's different with brain waves but what I told you is an I can tell you, so I'll go and there's no charge except for carfare."

He made as though to get up, but Dr. Cray was shaking her head vigorously.

"Please sit down, Mr. Bishop. Recording brain waves is different. There we do need all the detail we can get. Till now, all we've ever had out of brain waves are the tiny, overlapping effects of ten billion brain cells, a kind of rough average that wipes out everything but the most general effects."

"You mean like listening to ten billion pianos all playing different tunes a hundred miles away?"

"Exactly."

"All you get is noise?"

"Not quite. We do get some information-about epilepsy, for instance. With laser recording, however, we begin to get the fine detail; we begin to hear the individual tunes those separate pianos are playing; we begin to hear which particular pianos may be out of tune."

Bishop lifted his eyebrows. "So you can tell what makes a particular crazy person crazy?"

"In a way of speaking. Look at this." In another corner of the room a screen flashed to life, with a thin wavering line over it. "Do you see this, Mr. Bishop?" Dr. Cray pressed the button of an indicator in her hand and one little blip in the line reddened. The line moved along past the lighted screen and red blips appeared periodically.

"That's a microphotograph," said Dr. Cray. "Those little red discontinuities are not visible to the unaided eye and wouldn't be visible with any recording device less delicate than the laser. It appears only when this particular patient is in depression. The markings are more pronounced, the deeper the depression."

Bishop thought about it for a while. Then he said, "Can you do anything about it? So far, it just means you can tell by that blip there's a depression, which you can tell by just listening to the patient."

"Quite right, but the details help. For instance, we can convert the brain waves into delicately flickering light waves and, what's more, into the equivalent sound waves. We use the same laser system that is used to record your music. We get a sort of dimly musical hum that matches the light flicker. I would like you to listen to it by earphone."

"The music from that particular depressive person whose brain produced that line?"

"Yes, and since we can't intensify it much without losing detail, we will ask you to listen by earphone."

"And watch the light, too?"

"That's not necessary. You can close your eyes. Enough of the flicker will penetrate the eyelids to affect the brain."

Bishop closed his eyes. Through the hum, he could hear the tiny wail of a complex beat, a complex, sad beat that carried all the troubles of the tired old world in it. He listened, vaguely conscious of the dim light beating on his eyeballs in flickering time.

He felt his shirt pulled at strenuously. "Mr. Bishop-Mr. Bishop-"

He took a deep breath..'Thanks!" he said, shuddering a little. "That upset me, but I couldn't let go."

"You were listening to brain-wave depression and it was affecting you. It was forcing your own brain-wave pattern to keep time. You felt depressed, didn't you?"

"All the way."

"Well, if we can locate the portion of the wave characteristic of depression, or of any mental abnormality, remove that, and play all the rest of the brain wave, the patient's pattern will be modified into normal form."

"For how long?"

"For a while after the treatment is stopped. For a while, but not long. A few days. A week. Then the patient has to return."

"That's better than nothing."

"And less than enough. A person is born with certain genes, Mr. Bishop, that dictate a certain potential brain structure. A person suffers certain environmental influences. These are not easy things to neutralize, so here in this institution we've been trying to find more efficient and long-lasting schemes for neutralization…And you can help us, perhaps. That's why we've asked you to come here."

"But I don't know anything about this, Doc. I never heard about recording brain waves by laser." He pushed his hands apart, palms down. "I've got nothing for you."

Dr. Cray looked impatient. She pushed her hands deep into the pockets of her jacket and said, "Just a while ago, you said that the laser recorded more detail than the ear could hear."

"Yes. I stand by that."

"I know. One of my colleagues read an interview with you in the December 2000 issue of High Fidelity magazine, in which you said that. That's what attracted our attention. The ear can't get the laser detail, but the eye can, you see. It's the flickering light that alters the brain pattern to the norm, not the wavering sound. The sound alone will do nothing. It will, however, reinforce the effect when the light is working."

"You can't complain about that."

"We can. The reinforcement isn't good enough. The gentle, delicate, almost infinitely complex variations produced in the sound by laser recording is lost on the ear. Too much is present and it drowns out the portion that is reinforcing."

"What makes you think that a reinforcing portion is there?"

"Because occasionally, more or less by accident, we can produce something that seems to work better than the entire brain wave, but we don't see why. We need a musician. Maybe you. If you listen to both sets of brain waves, perhaps you can figure out by some insight a beat that will fit the normal set better than the abnormal one. Then that could reinforce the light, you see, and improve the effectiveness of the therapy."

"Hey," said Bishop in alarm, "that's putting a lot of responsibility on me. When I write music, I'm just caressing the ear and making the muscles jump. I'm not trying to cure an ailing brain."

"All we ask is that you caress the ears and make the muscles jump, but do it so that it fits the normal music of the brain waves…And I assure you that you need fear no responsibility, Mr. Bishop. It is quite unlikely that your music would do harm, and it might do so much good. And you'll be paid, Mr. Bishop, win or lose."