Some sites metion that he was only good playing his stuff. Is that ture?
I think that generalization has been made about the vast majority of composer/pianists. It's been said about Prokofiev, Ravel, Bartok, Beethoven, Shostakovich, Stravinsky, Saint-Saens ..... and pretty much everyone except for Liszt, Rachmaninov, and Chopin.Even Mozart played mostly his own stuff.
The cadenzas Brahms wrote out for keyboard concertos by Bach, and Mozart were published for the first time in 1927, while those for Beethoven's G Major Piano Concerto were published originally in 1907. The cadenza for Bach's Concerto in D minor preserves something of the style and figuration of the concerto itself. The manuscript of the cadenzas to Mozart’s Concerto in G major, K. 453, carries a note of attribution from Clara Schumann and is clear enough in texture, with one or two chords that demand either a large hand or arpeggiation. The cadenza for the slow movement is marked quasi fantasia and brings an element of Brahmsian cross-rhythm. It exists in alternative versions. The rather more elaborate cadenza for Mozart's Concerto in D minor, K. 466, was used, in part, by Clara Schumann, as her note on the manuscript informs us. Brahms himself played the concerto in Hamburg in 1856 for the Mozart centenary celebrations. The cadenza for the first movement of Mozart's Concerto in C minor, K. 491 also carries a note of authentication from Clara Schumann, in whose possession, it can be presumed, these manuscripts once were. For Beethoven' s Piano Concerto in C minor, Opus 37, there is a first movement cadenza of some elaboration which is wrongly attributed, the work of the pianist and composer Ignaz Moscheles, interesting as an elaboration by a pupil of Beethoven himself, however different in style. The cadenzas for the first and third movements of Beethoven's Concerto in G major, Op. 58, are testimony to something of Brahms's own technical accomplishment as a pianist. He played the concerto in Bremen and again in Leipzig in 1855, and was the soloist again in the concerto in Detmold in 1857, when his playing led to his appointment at court. These and the other surviving cadenzas are reminders of the early career of Brahms as a pianist and his continuing activity in the concert-hall, although Hanslick, a strong enough supporter, found that Brahms, later in his career, while always deeply interesting as a player, was not always equally accurate.
There is a amazing story: he was for a performance at a village of Beethoven's Kreutzer ( or Spring, I don't remember) with Joachim as a violinist.The piano was a tone upper so Brahms (not Joachim) without hesitating much, simoultaneously transcribed and played all the Sonate a tone down. It was much celebrated at his time. I think he was considered a great pianist .
While it is possible that he played some of his violin concertos, I doubt he could have pulled of his Op. 77 (Have you heard this? holy s**t).
.... or too lazy to practice as he should. Nevertheless he was at the stage along almost all his life.
I heard a story of him once. The story goes that he was premiering his violin sonata. Both the pianist and himself were both excellent at violin and piano. 10 min. before they went on stage they couldn't decide who would play what part. Therefore they flipped a coin to see and went onstage and performed it. boliver