Possible Clues:

• Regency architect from the north remains
• Partner of Crosby, Stills and Young
• "A Beautiful Mind" mathematician
• "Our House" songwriter
• Crosby, Stills & ___
• Crowe's 'A Beautiful Mind' role
• Musical partner of Crosby and Stills
• He wrote 'If called by a panther, / Don't anther'
• Ogden or Graham
• Metropolitan maker?