How bluesy is Ravel's Blues actually?
I would say enough to justify putting "blues" in the title of a violin sonata.
A little history background.
WC Handy published the "first blues" music in 1912 with Memphis Blues. The style is basically ragtime in rhythm and piano texture and uses chromatic approach tones (like
B natural ascending to
C of an
F major chord) and dominant seventh chords on roots other than
Stravinsky's Rites of Spring was first performed in 1913. That's a seminal work of modernism and dissonance.
Ravel's Violin Sonata No.2 is dated 1923-7.
Gershwin's Rhapsody in Blue is from 1924.
All of that is from before musicians like Muddy Waters or BB King were born or were still kids.
We need to understand what "blues" meant at the time for Ravel. To a listener today the blues from that time would probably be labeled "ragtime."
The IMSLP copy of the score is dated 1927 and has "blues" printed on the second movement. So clearly Ravel had some intension of the music being bluesy.
But to what extent? What does the music itself tell us? Notice how the movement opens. The key signature of the violin is one sharp and the piano is four flats. Neither is a transposition instrument. When the piano first enters the violin plays pizzicato
G major chords while the piano outlines an
Ab major chord. After the intro the violin changes to a key signature of four flats, but then the piano takes over play the
G major chords against
Ab. It seems noteworthy the movements starts with a kind of modern, polytonal harmony. Regardless of other bluesy elements in the movement it is not following the style of early blues like Memphis Blues.
...is that because of a lack of understanding of the blues...
I don't think so. If Ravel wanted to just write something like Memphis Blues, he could have done so. But composers like Ravel were more "referencing the blues" rather than cranking out genre pieces. At the risk of sounding pretentious it's the difference between "low art" and "high art." Low art being stuff like a set of waltzes or rags that follow the template of a genre, usually for some real social function. Basically songs and dances that people actually danced to. High art is stuff like sonatas and fugues. Music meant to be listened to and appreciated on some intellectual level for the way themes are handled and developed musically.
Other composers made music like Ravel's with references to blues and jazz. Things like Stravinsky's Ragtime, Bartok's Contrasts, Gershwin's Preludes, Debussy's Golliwog's Cakewalk, etc. Some of these works are closer to the song/dance forms (IMO Gershwin's preludes and Debussy's cakewalk) while others are more in the intellectual concert music vein. It's interesting how some like Gershwin aimed high seeking recognition as "serious" composers while others wanted to incorporate popular forms in concert forms.
...or the same attitude of the 19th-century "exoticism" craze which was far from authentic
Of course "authenticity" is the real heart of this question. But what is going to be called authentic blues? If you go back before Memphis Blues you get to stuff like field hollers. Call and response folk music with blue notes. When WC Handy set those elements into a basic ragtime style how is that any more or less authentic an appropriation than Ravel setting them within a modernistic violin sonata?
Clearly Ravel's sonata is a high art concert piece and not song or dance. But calling it inauthentic is a tricky business, because it seems to arbitrarily allow certain types of musical appropriation while excluding others.