Hearts have insisted The Sash "has no place at Tynecastle" after the song was played at the stadium during a club open day.
Footage emerged on social media showing the well-known loyalist tune blaring as fans toured the stadium.
It happened during the Foundation of Hearts open day event where fans were given access to the Tynecastle facilities
But there appeared to be an interruption as video footage showed the song playing loudly over the PA system.
The club have now concluded their investigation into the incident and issued an apology to those who were at the ground, and to the wider Hearts fan base.
A statement from the Edinburgh side read: "During the day’s festivities, an incident occurred whereby a song was played over the PA system.
"The song in question has no connection to Hearts and it has no place at Tynecastle.
"As soon as the club was made aware of the issue the PA system was switched off, the incident investigated and swiftly concluded.
"Club officials apologised at the time to those inside the stadium who brought the matter to their attention.
"The club would now like to further extend that apology to our wider fanbase after videos of the incident were shared on social media.
"Procedures have already been implemented that will ensure such an incident is never repeated.
"The FoH Open Day was an extremely proud occasion for the club and we would like to, once again, thank our supporters who continue to back every aspect of the club in tremendous fashion.
"We look forward to welcoming everyone back to Gorgie for this Saturday’s cinch Premiership encounter with Dundee United."
