Formally submitted by the Royal High School Preservation Trust (RHSPT) in December last year, officials said the plans to bring the A-listed building back into “long-term, sustainable future use” would be a “significant conservation gain”.

A report to go before the City of Edinburgh Council praised the sensitive approach by Richard Murphy Architects and Simpson & Brown, who were appointed to develop proposals for the restoration in September.

The proposal was launched as an alternative to a £75 million luxury hotel plan for the neoclassical building by Duddingston House Properties.

This Hoskins Architects-designed bid was formally dismissed by a single vote last year, though an appeal to the Scottish Government is scheduled to begin on November 28.

The latest application, set to go before councillors next week, aims to transform the site into a concert venue and base for St Mary’s Music School. The proposals include a performance space located in the main hall of the Hamilton building and two ancillary rooms, and a “glazed slot within the portico floor of the Hamilton building” and “glass balustrade on the terrace to the portico”.

New single-storey accommodation is also proposed for the site and demolition of the existing classroom block to the north west of the Hamilton Building and the gymnasium building to the north east of the Hamilton Building.

Council planners stated on balance that the RHSPT would have “no adverse impact on the architectural integrity and composition of the building”.

However, it is understood a contract between the council and Duddingston House Properties would not be affected if councillors gave the music school plans the go-ahead.

This means the RHSPT could be unable to act on their blueprints until 2022, when the council’s contract with Duddingston ends – even if the hotel developer’s current plans fail on appeal.

Duddingston entered into a contract with the council five years ago after they won an open competition to develop the site.

William Gray Muir, chairman of the RHSPT, said: “For a proposal of this significance it is remarkable that there were only four objections, compared to more than 500 people and groups who took the trouble to write in support.”