Claire Jones played a specially composed piece as the King and the Queen Consort made their way through the Senedd to hear a motion of condolence.
The piece, Gorymdaith i’r Frenin Siarl, which means A Procession for King Charles, was written by Ms Jones’s husband Chris Marshall.
Joining her in playing were Cerys Rees and Nia Evans, from the Royal Welsh College of Music and Drama.
“It was such a privilege to be his official harpist for four years and during that time I performed over 180 times for the royal family, including one-to-one for Her Majesty the Queen and for many state occasions for Her Majesty over the years,” Ms Jones said.
“The performance at the Senedd was a very special moment as I performed my husband’s music for His Majesty King Charles.”
Mr Marshall said: “I am truly honoured to compose this special work for such a momentous occasion, the arrival of King Charles III in Wales.
“The music is a stately, sombre procession which represents the ascension of the monarch to the throne.”
Ms Jones is one of Britain’s best known classical harpists and served as the official harpist to Charles as Prince of Wales between 2007 and 11.
She became a household name for her performance at the wedding of the new Prince and Princess of Wales.