He became editor of the British Traveller and Commercial and Law Gazette, a London evening paper, in 1833, and in the same year managed the foreign department of the Morning Post, and also a sub-editor.
[1] Gruneisen was present at the Carlist victory at the Battle of Villar de los Navarros, 24 August 1837, intervening to prevent harm to prisoners.
[1] On his return to England Gruneisen acted as music critic to The Britannia, the Illustrated London News, and the Morning Chronicle, to 1853.
He succeeded Charles Cowden Clarke in 1868 as music critic of The Athenæum, a position he held for the rest of his life.
[1] The Royal Italian Opera was established at Covent Garden in 1846, with Michael Costa as conductor; it was backed by Gruneisen, who had helped to plan it.
In 1869 he publicly expressed dissatisfaction with the management of Frederick Gye; who broke with Gruneisen and entered into partnership with James Henry Mapleson.