By Friday afternoon, a fortnight after 13-year-old gospel singer Tyrone Ford had vanished, his grandmother was distraught. She pleaded in front of a television news crew, asking for help in finding the precocious performer who had been called a hero by President Reagan.

But just after midnight, when Ford called his Rock Creek Church Road home saying he was being held captive, bound and guarded by a Doberman pinscher, his grandmother would not go to the phone. She said she knew that he was lying -- that he had been hanging out with his streetwise friends. And a few hours later, Ford admitted it.

"People think I'm hanging around the wrong crowd," he said Saturday. "I think I'm hanging around the wrong crowd. My friends hang around the street a lot. I'm going to cool down and get away from them," to get back to the church and his music.

Music had taken Ford a long way. A year ago, at Reagan's State of the Union address, Tyrone Ford sat with the heroes.

At 12, he was already choir director at three Washington churches, a veteran of concerts at Wolf Trap and the Kennedy Center, dubbed by Washingtonian magazine as "the Wonder Boy of gospel music."

Introducing Ford last year, Reagan said, "We see the dream glow in {his} towering talent . . . . With God as your composer, Tyrone, your music will be the music of angels."

But since that time, Ford "just made a 180-degree change," said the Rev. Walter Coles, a preacher at Fellowship Baptist Church in Northeast. "He was an all-around nice American boy, and now he seems to be leaning toward the outside world."

Burter Carelock, Ford's grandmother and legal guardian, said Ford had been with friends whom he hoped to impress with money. These friends, Carelock alleged, are older and into drugs and alcohol.

Ford insists that neither he nor his friends use drugs.

Just before Christmas, Carelock discovered that Ford had exhausted his $1,400 bank account, spending some of the money on rented limousines.

This year, she said, she learned that his grades had dropped to Ds and Cs, and that he had failed one course that he is now making up in summer school. And later she discovered that in a single month, he had skipped more than 10 days of school.

"He went from clean clothes to dirty clothes. He had a sense of pride about himself, and then he lost all of that and didn't care how he looked," Carelock said.

"I could tell something happened to Tyrone when he didn't care whether his shirts were pressed. Then I knew something was breaking down Tyrone."

Coles said Ford, choir director at the church, had not attended the last choir performances or rehearsals and no longer attends Sunday school.

In the past few months, Carelock said, Ford began going home late, sometimes not until after midnight or not at all. Then, late last month, he vanished for four days.

That was the first time that his grandmother called the police; but as on Saturday, Carelock said, he went home on his own after he heard that police were looking for him.

This time, despite his kidnaping claim, Ford strolled casually in, shirtless, off the street.

Avoiding relatives who were waiting on the front steps, he walked directly to a police car, where he unfolded his story.

Ford initially said that he had been abducted by two men who drove up beside him as he was walking home from school two weeks ago.

He said the men took him to a house in Oxon Hill, bound his hands and left him in the basement with the guard dog.

He said that after he got free and called home, he hitchhiked back to his house. But when he was questioned by police, Ford conceded that he had not been abducted. Eventually, he showed police where he had been staying -- a friend's house, less than a mile from his grandmother's.

Saturday afternoon, things at Ford's home seemed almost back to normal. Sitting at the piano, a few feet from his grandmother's recliner, Ford played his favorite song, "This Little Light of Mine," a gospel number he learned when he was 6 years old. As he played, his grandmother recalled how she used to complain when he played the song over and over again. Now, she hopes, it will rekindle the light in Ford.

"He told me that God gave him 'This Little Light of Mine,' so I told him if God gave it to him, I wasn't going to take it away."