Ray Charles At Republican Party Convention In 1984

 The Raegans applaud Ray at the
inaugural ball on Jan. 20, 1981. 

 Ray & the Reagans at Constitution
Hall, in 1983. 

The Beeld- & Geluid-Archief holds a fragment of the Dutch public broadcasting's prime time news cast, the NOS Journaal, of 24 August 1984, where Ray sings America The Beautiful during the Republican Party Convention, described in their database as "Reagan and Bush on stage, applause, Ray Charles sings".
NBC covered Ray Charles at least three times during the event. According to NBC News Archives (ID T840824, N840824) Ray was seen playing "[...] God Bless America [sic!] on the piano".

On 24 August NBC had a 5m30s item (ID T860728) on Ray. Synopsis: "Musician Ray Charles discusses his career - part 1 of 2. In interview black musician Charles says he doesn't think of himself as a blues, country & western, or jazz singer, but as a good utility man. He states he could'nt stay away from music as a child. Charles sings & plays piano in concert. He compares singing to acting & asserts both involve a deeply felt emotion. He states he likes a lot of songs although that doesn't mean he can sing them. Charles claims he likes to do songs his own way adding the final criterion in choosing a song is whether or not it moves him. On 8-24-84 Charles is seen at the Republican Convention with VP Bush & Pres & Mrs Reagan. Charles sings America The Beautiful". [See comment for correction on the quoted date].

After acceptance speech at GOP
Convention in Dallas on Aug. 23, 1984.

After his appearance at the 1984 convention, Charles also played at the subsequent Inaugural Ball. And in 1986, Reagan and his wife attended the Kennedy Center Honors ceremony in which Ray Charles was one of the honored artists.

Ray wasn't picky with the presidents he performed for. Watch this. And this. And this, this and this. Ray has explicitly stated several times that he talked with presidents to lobby for the charities he supported, and that he played for them because he was paid for it.

Ray Charles and Ronald Reagan have crossed paths more than once. Charles worked with Reagan during his first term on disability issues. Soon after Reagan took office in 1981, he signed a proclamation for the Decade of Disabled Persons. Reagan then helped launch the National Organization On Disability's Ad Council campaign, which featured Ray Charles.

America The Beautiful:

Afterwards they schlepped Ray around in triumph (sequence starts at 2:19:50):