Thaddeus Kearse worked with the ivory keys of the old, upright piano. The piano was out of tune but the tin souding notes went unnoticed because of the feeling and emotion of the song and performer.

The notion that beauty and harmony can come from slightly worn and damaged material seemed obvious to the room full of foster parents from all over Prince George's County. It was a notion they have to deal with every day of their lives, every time a new child is brought to them, every time an older child is taken away.

The Prince George's County Department of Social Services, Lutheran Social Services and Catholic Charities honored their foster parents last week with a program of song, dance, welcome and awards. The piano player, Kearse, 16, is a foster child.

More than a hundred parents came to the festively decorated, multi-purpose room of the Ascension Lutheran Church in Landover Hills. Dressed in their Sunday finery, some toted infants in swaddling clothes, others brought older children, some their own, some only theirs for a little while.

"All of us as parents would agree it is not an easy task to raise children," said Barbara Hoagwood, supervisor of the Department of Social Service's Adoption and Foster Homefinding Unit. "And raising someone else's children, those who have more bad memories to overcome then they have years in some cases, is even harder. You people are bringin to life the dictationary defintiion of foster to cherish, harbor fondly in your mind."

Six "superparents" were picked from the more than 375 foster parents by their agencies to receive Outstanding Foster Parent Awards. Prince George's County Executive Winfield M. Kelly Jr. and Del. David Ross (D-Prince George's) presented the awards to the group at the end of the program. Nominated and chosen by their caseworkers for special "warmth, loving and giving" or just for being "able to love and let go" as Hoagwood said, the parents joined those awarded for five, 10, 15 and 20 years of service at the awards ceremony.

"My husband's been asking me all week, 'Are we really that outstanding, are we really that different?' laughed one recipient, Carol Norman. A foster mother of two-and-half years and mother of three children of her own, she smiled and rumpled the soft blond hair of the 3-year-old foster child she was holding. "It's nice being a foster paretn. But we are a foster family. It couldn't be done without them."

The Normans decided to become foster parents after their children were in school. "I asked myself, what did I want to do with my time?" said Mrs. Norman. "We talked it over and decided where the Lord was directing us. I am in it mostly to help families be families."

The recipients of the Catholic Charities award, Mrs. and Mrs. Francis Blake of Takoma Park, have four children in their home, in addition to their own three. They also received an award for being foster parents for five years. "We now have all the members of one family in our home," said Mrs. Blake. "We would like to keep the group together and see them grow up (through adoption), but others are in need, too. We could have adopted, but we felt our services would be more beneficial if we stayed foster parents."

The strong attachments formed between foster children and their surrogate parents occasionally lead to adoption. More often, the attackments become part of the price of being a foster parent when the child is taken away. Mrs. Norman recalled that their first child was with them two-and-a-half years before adoption. "Sure it was hard when the child left us because the sooner they are placed, the easier it is. But we know the need of other children is there and we get over it."

Other winners of Outstanding Parent Awards were Perry and Harriet Crabill of Bladensburg, Danny and Nancy Swindell of Clinton, John and Ethel King of Cinton and Donald and Mary Corrigan, who received their award from the Lutheran Social Services.

"Call it the above-and-beyond-the-call-of-duty award," said Marcia Zvara, director of the Adoption, Foster Care and Single Parent Service Buraue. She said foster homes provide a child with "a feeling of belonging, even though we're well aware they'll be taken away.

"Foster care is an alternative for a child while we determine if the home is reasonable," said Zvara. Children go into foster care "through police referral, suspected abuse, through parents who say 'we just can't cope with these kids,' or if one parent is managing alone and becomes too ill for proper care."

The department has two kinds of homes for foster children, a regular home where children come and go as vacancies arise, and restricted homes, where the parents are interested in caring only for a specific child. Zvara stressed the need for more foster parents, adding that homes for teen-agers and for large groups of children from one family are particularly needed.

Foster parents cross all age, race and religious barriers, reflected by many of the persons attending the program. Robert andTheresa Martin of Lanham have been foster parents for 10 years. Mrs. Martin, an energetic 69-year-old, retired from the telephone company 10 years ago and became involved with foster care through her church. She offers encouragement to other older people to become foster parents.

"It's the best thing a person of my age can do," she said. "We have been married 50 years and have talked ourselves out to each other. This gives us something to focus on." Mrs. Martin adds that she has children, grandchildren and great-grandchildren but "it's so rewarding to have the little ones. We take the smaller children, 2 and 3 years old. They wanted us to take teenagers, but it wouldn't be fair to them or us to take them in. We're too old-fashioned for that age. We love the small ones and the little kids are so grateful."

In a brief speech, Del. David Ross, a former foster parent himself, discussed new state legislation affecting foster care. "But mostly," he said, "I came because I wanted to be with you."

As many of the caseworkers and onlookers nodded in agreement, he concluded, "I came simply to honor you. There is no greater tribute we could pay to you."