It can be misleading to put too much emphasis on exact determinations of what constitutes one thing or the other in classical music, at least as far as musical form goes. Imaginative composers rarely held rigidly to textbook examples. Indeed, some composers were actively using and varying musical forms before there were textbooks on the subject. There are accepted examples of all the basic forms used in music, but it is good to remember that these should serve as models, not laws that must be obeyed at all costs. Variation is basic to the art of music, so why would imaginative composers not do the same as far as form and structure?
So what makes Alkan's work (as well as Bach's) a valid concerto? In Bach's case, the two-manual harpsichord can provide the differentiation in sound to help create the impression of a concerted work for one instrument. But in modern times Bach's work is also played on the piano, an instrument of but one keyboard. But under the sensitive fingers of a good pianist the piano can convey a number of differences in timbre, volume, and articulation. Add to that the creative use of the piano pedals and the instrument can bring off the solo concerto concept. Not with the depth of tone color as an orchestra, but the piano is more than capable of countless gradations from black to white and all the grays in between. With such an expressive and versatile instrument benefiting from the writing of an imaginative, master composer such as Alkan, the solo concerto is a possibility.
Alkan was a recluse for many years and his music suffered from neglect, at least from most main stream pianists. There have always been some pianists and composers that knew of his works, but the real revival of Alkan's works began in the last years of the 1960's. With landmark recordings by the pianists Raymond Lewenthal and Ronald Smith, Alkan's music is now back in the repertoire, at least for the pianists who can play it. Many of Alkan's works are very difficult technically and musically, which no doubt led to their neglect for many years.
I. Allegro assai - The first movement is the eighth etude of the 12 Etudes In The Minor Keys. It begins in the key of G-sharp minor with a section marked quasi trombe (like trumpets). This first theme is followed by a second contrasting theme. Following the second contrasting theme, a third theme of a more robust nature makes its entrance. A short return to the opening material rounds off what constitutes the orchestral part of the exposition. The soloist part enters with runs up and down the keyboard and the exposition continues with the return of all three themes in expanded form. The development section of these themes runs far afield in mood and texture, and with just a little effort a good listener can begin to 'hear' the entities of soloist and orchestra take shape. The harbinger of the recapitulation appears as a persistent G-sharp, sometimes in the treble, sometimes in the bass. The recapitulation brings back the three themes, and then a section marked quasi-tamburo (like a drum) transforms the first and second subjects into a wildly rhythmic treatment that continues with the pianist using the third finger of each hand to hammer out a steady stream of alternating sixteenth notes in rapid tempo. The second theme appears over the sixteenth notes as it winds down to a repeat of the first theme in high chords of the treble accompanied by the bottom notes of the piano. A tremendous crescendo occurs, Alkan writes the key signature of A-flat major, the enharmonic equivalent of G-sharp major, and a short section brings back the trumpets of the beginning and the movement ends with a wide spread A-flat major chord. This first movement takes almost 30 minutes to play, consists of over 1300 measures, and taxes the technique and endurance of the pianist to the extreme. It is also a challenge musically. As if all that wasn't enough for the listener and pianist, there are two more movements to go.
II. Adagio - This is the 9th Etude from the set and as Alkan progressed by a perfect fourth through all the minor keys, it is in C-sharp minor. The opening is marked quasi-celli (like cellos). The orchestra plays a melancholy introduction to the theme that is taken up by the soloist. A second theme is in the major and is contrast to the opening. A short section for single unaccompanied notes leads to a section of a different character all together, a somewhat light-hearted tune that leads to an impassioned, agitated repeat of the first theme which leads to yet another different section punctuated by a drum beat rhythm in the bass. The light hearted tune alternated with the drum beats until the opening theme returns once again but is soon interrupted by the drumbeats. The melancholy introduction appears, the drumbeats quietly interrupt one more time. The first two measures of the first theme are played over the quiet drumbeats. A strongly accented triple forte C-sharp minor chord widely spread between both extremes of the keyboard end the movement.
III. Allegretto alla barbaresca - The 10th Etude from the set in F-sharp minor begins with a huge rolled chord for both hands and a 4 bar motive that appears throughout the etude, sandwiched between some incredibly different sections. The entire etude is one of movement and themes that are presented with abandon. There is an impelling forward movement in the music that is apparent even in the calmer sections. The work ends in a deluge of manic intensity and bravado in F-sharp major.
Ronald Smith is the pianist in the accompanying video. I first heard his recording of this work on long playing records many years ago. Since then there have been other recordings of the 12 Minor Key Etudes, and along with the recording by Ronald Smith I especially enjoy the recording by Jack Gibbons, an English pianist who was the first to perform all 12 Minor Key Etudes in live concert at Oxford in 1995.