"He played so beautifully," said Rivera, who had read about Nathaniel and knew he had been diagnosed in the 1970s with schizophrenia while a student at Juilliard. "I really love Los Angeles, and sitting there watching him as all these cars were whizzing past, with helicopters going by in the shadow of Disney Hall -- if you took a video image, it would perfectly capture the city."
Nathaniel was taken aback.
"He said, 'What? Nobody has asked me to do that in 30 years.' "
Nathaniel expressed doubts, saying he was too dirty to do a show, and there'd be nowhere to put the shopping cart that contains all his belongings.
It took about 15 minutes for Rivera to persuade Nathaniel to serve as an opening act on Tuesday nights, from 7 to 9, for rhythm and blues singer Mickey Champion. Rivera told Nathaniel if he got there early, he could have dinner for free.
" 'If I have dinner before I perform, I'll throw up,' " was Nathaniel's response, Rivera said.
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On that first Tuesday, Nathaniel ran so late, Rivera wondered if he'd forgotten. When he finally arrived, Nathaniel seemed very nervous and took so long tuning his violin he never started. Shannon Murray of Lamp, the skid row mental health services agency that has been reaching out to Nathaniel, used her usual perfect touch in consoling and encouraging Nathaniel.
"I was horrible," Nathaniel later told me, but he said he was eager to do better next time. In fact, he said, he was putting in lots of practice time.
I arranged for a couple of psychiatrists to watch his next show with me at Little Pedro's, not just to get their assessment of Nathaniel, but because California is on the verge of the greatest growth of mental health services in four decades. Under Proposition 63, which voters approved in November, more than $700 million a year will be available statewide to expand and improve mental health care.
Darrell Steinberg, the former state assemblyman behind Proposition 63 -- which put a 1% tax on Californians with income over $1 million a year -- believes that if the money is spent wisely, the state can make a huge dent in homelessness caused by mental illness and begin to relieve the suffering of both the mentally ill and their tormented families.
"We have a historic opportunity to help a lot of people who have been ignored," Steinberg said. In Los Angeles County alone, the homeless count is estimated at 90,000.
The new money is "the most important thing to come along in 40 years," said Dr. Roderick Shaner, who joined me at Little Pedro's and is medical director for the Los Angeles County Department of Mental Health.
Shaner, who is helping to prepare the county's plan for spending an expected $100-million annual shot in the arm, said some of that money would go toward efforts to cajole people like Nathaniel off the streets and into therapy and housing.
But he realizes there are no easy cases, and Nathaniel provided the latest proof. As 7 p.m. came, the stage at Little Pedro's was empty.
Had Nathaniel forgotten?
When 7:30 rolled around, Vera Prchal, a Lamp psychiatrist, seemed as concerned as I was, and she hadn't even met Nathaniel yet.
Just before 8, I decided to go look for him in his usual skid row haunts. I was losing hope. But Nathaniel was already on his way.
A block from Little Pedro's, I saw the familiar shopping cart, which is festooned with palm fronds and contains a Ford hubcap, two violins, a cello and the sticks labeled "Beethoven" and "Brahms" that he uses to scatter rats when he beds down for the night.
"I had another engagement," Nathaniel told me without explanation.
Nathaniel left his cart in the parking lot, where Rivera had a watchman keep an eye on it, and strode into Little Pedro's with all three of his instruments. Eight or 10 patrons were waiting when he finally took the stage.
There's both madness and dignity in Nathaniel's appearance. He's got matted hair and grimy layers of clothing, including a sweat shirt tied around his waist to conceal a wooden club he carries in anticipation of someone attacking him on skid row. But he is meticulously neat to the extent possible, and he moves with polite bearing that suggests formality and respect.
He tuned his violin for several minutes, reacted somewhat nervously to a warm round of applause upon being introduced, and began to play.
I've heard better, more passionate playing from Nathaniel. He seemed tentative and at times turned away from the room, as if he was too uncomfortable with his own performance to face his audience. Performing here in this setting, with people focused on him rather than walking or driving past, must have been both thrilling and terrifying.
He began with something Beethoven-like, as he had planned, but seemed to lose the thread. Nathaniel is inspired and haunted by music and his history with it -- a history scrambled, interrupted, incomplete. More than once, he apologized to the audience.
I could only wonder at what was going through the mind of this man, who 30-plus years ago studied bass in New York City as a young phenom from Cleveland. I've talked to his friends of that time -- people who saw great promise unravel as Nathaniel's mind began playing tricks on him and the music he revered seemed ever more elusive.
After switching to cello at Little Pedro's, Nathaniel was still a bit disorganized but much more comfortable, and there were moments when both his music and his expression -- head thrown back in pained delight -- were things of beauty.
Dr. Shaner later called it tragic that Nathaniel, or anyone who is chronically mentally ill, is left to live on dangerous streets. The civil rights concerns that led policymakers to empty the state's mental hospitals over the last three decades were well-intentioned, but the move helped create today's problem. Society has failed to deal with the stigma and destructive reality of mental illness.
"I'd like to seduce him into treatment, and he needs seduction," said Dr. Prchal. She said it wouldn't be easy -- Nathaniel needs medication as well as counseling on how to pull his life together. But there is greater success with those who -- like Nathaniel -- have no addiction problems, Prchal said.
"People with his IQ, tremendous ambition and achievement don't like to be ordered around. But this man has to be treated. I will try to meet with him and slowly start some dialogue about the possibility of treatment, and slowly also see if he would want to have his own room, maybe if only to store his instruments at first."
When I spoke to Nathaniel after his performance, he bowed his head and apologized.
"I was really, really bad in there," he said.
I encouraged him and handed him the tips that had been left. He said he wasn't worthy, but I folded the money into his hand and asked if he'd return the following Tuesday, an offer Pedro's owner Alexis Rivera is happy to extend.
"If they're interested in having me back," Nathaniel said, "I'll be here."
Reach the columnist at email@example.com and read previous columns at www.latimes.com/lopez.