HOUSTON — Some of President George H.W. Bush's favorite country music stars performed at his funeral in Houston Thursday.

Many Bush family members sang along as Reba McEntire performed "The Lord's Prayer" at St. Martin's Episcopal Church.

WATCH: Reba McEntire sings "The Lord's Prayer"

The Oak Ridge Boys sang "Amazing Grace," keeping a promise they made long ago.

Duane Allen of the Oak Ridge Boys says Bush had personally requested the group sing "Amazing Grace" at his funeral.

RELATED: Oak Ridge Boys kept promise to President Bush: 'It's what you do for friends'

Group members have taken a suit and tie everywhere they’ve gone for the last couple of months in preparation for the call members knew was coming sooner than later.

“It’s what you do for friends,” said the Allen told the Nashville Tennessean

The group has been in talks with the Bush family to participate in Bush’s final proceedings for six months, but the call came three or four weeks ago that his condition had deteriorated further.

RELATED: Athletes, actors among mourners at Bush 41's funeral

Allen’s relationship with Bush dates back to the 1960s when the singer and his friends were hired to distribute flyers promoting Bush, who was then running for office in Texas. In the 1980s,

Allen tells The Tennessean newspaper the band did an impromptu performance for Bush at the White House when Bush was vice president and that began a decades-long friendship.

Several star athletes and actors were among the 1,200 mourners who attended Thursday's funeral.

The Nashville Tennessean contributed to this report.