Thank you all for your suggestions. Most of us, including myself, think Brahms with the grandiose opening of his PC #1 carries off the honours, like Peter says. And yes, of course, Beethoven #4 but also #5. And Rachmaninoff #2...For our unsung heroes I keep thinking that it’s all a matter of personal taste.
Ilja mentions a few Scandinavian (?) composers I have never heard of, but also Scharwenka #1. I love all his 4 PC’s but prefer #4, not only for the opening but also the beautiful 2nd movement and the thrilling finale.
Orff, I still haven’t heard the whole Huss PC, but listened to the opening on Hyperion’s website. Definately an explosive piano entry!
Talking about Hummel, I have his op. 110 played by the London Mozart Players with Howard Shelley, but I find many concertos, how brilliant they are and full of delightful themes, somewhat too classical, except for his op. 85&89, both with very elegant openings. Like I said, it’s a matter of taste.
I agree with Yavar. One of my favourites in Hyperion’s series of Romantic PC’s is Kullak. A subtle opening followed by captivating themes. What a pity that this splendid and brilliant work is the only music of Kullak on CD. He must have been a very interesting and creative composer as well.
I am not yet familiar with the Castillon. Alan, I agree with you on Reinecke's #3, but I prefer his #1. Yes, Litolff #4 features an opening which is hard to forget, just like the story of his adventurous life. And of course, the opening of Raff’s PC is delightful. I don’t know Ponti’s playing, I have the Aronsky. And has anyone heard the catchy opening of Tomášek’s PC #1?
In summary, there are a lot of unknown PC’s to be explored by me. I’m very much looking forward to the coming release of Benedict’s PC’s. Hopefully with superb openings…
But so far the Henselt is still my unsung favourite, and not only because of the stunning opening (I like it even more than Rubinstein #4…).