There are books about the Boston Symphony Orchestra that mention him. He played harp as well as piano. He won 1st prize in harp at the Paris Conservatoire, and in piano the next year. He read new scores at the piano for maestro Koussevitzky. There are many archives I am sure dealing with Koussevitzky and the BSO, not to mention Tanglewood. I met your grandfather in 1980 at Tanglewood, which was one of his last seasons. His hands were very large and powerful looking, yet completely relaxed. I remember hearing him play. The BSO may have an archivist, and you can also check newspaper and periodical indexes. Louise Pappoutsakis was his second harpist, followed by Ann Hobson. Good fortune in your search.