He was for a time politically associated with Lord Randolph Churchill, Sir Henry Drummond Wolff and Sir John (then Mr) Gorst, the quartette becoming known as the "Fourth Party," and gaining notoriety by the freedom of the criticisms directed by its leader, Lord Randolph Churchill, against Sir Stafford Northcote, Lord Cross and other prominent members of the "old gang."
He appeared in public as a violinist, taking part in Chappell's quartette concerts, and starting a set of classical concerts.
The most important compositions of this period of Mackenzie's life were the Quartette in E flat for piano and strings, Op. 11, and an overture, Cervantes, which owed its first performance to the encouragement and help of von Billow.
At the visitors' request the young people sang the quartette, "The Brook," with which everyone was delighted.