Least flashiest/technically demanding concerto in the repertoire?

[Luke]

The cadenza however sounds harder than it is.

Also true. It's no harder than the Schumann IMO

[Iota]

The opening theme in octaves of the Rach 3 is pretty easy; it's just the remaining 45 minutes -

I was bumming around backstage in the Royal Festival Hall before an Ashkenazy recital in the 80's sometime, and somehow got introduced to Ashkenazy's daughter. She took me onstage to look at the piano (bathed in light and in a hushed auditorium before people were let in, quite striking ..), and I asked her if she played a lot, and was quite shocked when she said she only knew how to play one thing, which was the opening bars of Rach 3. But if you're only going to choose one thing then that magical evergreen melody certainly isn't a bad way to go.

I agree the Grieg cadenza is a relatively little effort/high reward thing.

[Karl Henning]

I agree the Grieg cadenza is a relatively little effort/high reward thing.

And of course, there's nought wrong with that.

[Iota]

And of course, there's nought wrong with that.

No indeed, the more the merrier. Some other non-concerto piano examples that spring to mind are the Brahms G Rhapsody, Chopin Etudes Op.10 nos.4 & 12, and Op.25 no.1, but as with all such things, that hard part is playing them 'well' rather than just technically executing them.

[pjme]

Not in "the repertoire" - but definitely not flashy or technically very demanding 

Jean Francaix' miniature piano concertino....  

Jean Françaix achieved international success in 1936 with the first performance of his Concertino for piano and orchestra at the chamber music festival in Baden-Baden. During the ensuing years, the composer extended his oeuvre with numerous works in a wide range of genres including operas, ballets, orchestral works and also solo concertos, film music and vocal works. The composer also focused intensively on chamber music. Françaix taught at the Ecole Normale de Musique in Paris from 1959 to 1962. He participated actively in concert life, frequently together with his daughter Claude as partner at the piano, right up to shortly before his death on 25.9.1997 in Paris. (Source : Schott)
Claude Françaix recorded the concertino with Antal Dorati for Philips.

[atardecer]

The Dvořák piano concerto is not flashy but some say is difficult to play.

I came across this quote regarding the Dvořák piano concerto:

"In discussing the piano music of Franz Liszt, the pianist Leslie Howard, who has recorded all of it, notes: "... there is nothing in Liszt that is anywhere near as difficult to play as the Dvořák Piano Concerto - a magnificent piece of music, but one of the most ungainly bits of piano writing ever printed." "

[Jo498]

I don't buy that the Schumann and Grieg are less difficult than e.g. Mozart's or Bach's keyboard concertos. They certainly sound far more flashy (just think of the effective openings of the first movements), so regardless of difficulty they are not good examples for "unflashiness".

[Atriod]

If I understand the question right, I'm thinking the Schumann Piano. One pianist told me the cadenza was the easiest she knew.

While this may be true for the fingers (not entirely convinced it's actually easy, there are several sections that are marked pianissimo and are difficult to play, this is not easy to pull off simultaneously), it's a difficult concerto interpretively. Schumann's instructions are sometimes counter to the notes that are written. The pianist has to strike a fine line between virtuosity and lyrical playing. I've heard more mediocre performances than great whereas the truly arduous concertos like Lutoslawski has many great performances. More clues (to me) that it's not the typical concerto is Schumann not leaving the cadenza up to the performer and it originally not being intended as a concerto.

[atardecer]

"A phrase which would seem very simple in Haydn or Beethoven, becomes horribly difficult in Mozart. Really difficult! I've not yet found the key to Mozart." - Sviatoslav Richter