I am not sure why, because I don't usually dig deeper for info about musicians more than a peripheral/singular google search, but the more I dig, there are a few more hints around... like that he did 28 records/singles/albums and someone made a compilation of him and Johnny Meyer (13 songs, more folksy/traditional nothing classical).
He died quite young at 68... his obituary:
Last Friday, Dutch accordionist (and accordion pioneer) Harry Mooten
died. I've translated the obituary from today's Volkskrant below:
==========================
Harrie Mooten (68)
A musician that sought for recognition for the accordion
A working class boy from Amsterdam that created a festive atmosphere
at parties, but also a driven craftsman that won an Edison [a Dutch
Grammy] with his interpretations of Bach and other classical
composers. The musical life of accordionist Harry Mooten (age 68),
who died last Friday from a serious illness, was mainly devoted to
the recognition for his instrument.
Until long after the war, the squeezebox was viewed as a musical
instrument that could only be used to start a polonaise. By his
switch from entertainment to classical music, Mooten in the
sixties and seventies brought the accordion in vogue even at the
conservatory.
'I hope to be an example for people who also want to try to get
something refined out of their accordion', he said about that.
The self-taught man Harry Mooten won awards both for his popular
interpretations and for his classical renditions. In 1969 he
was awarded an Edison for his 'light' work, in 1972 for his records
with pieces by Bach and Beethoven. Apart from that, he made five
records with light jazz music.
Mootens talent came to light early. Already at the age of seven he
played banjo and appeared on VARA radio. At the age of nine he switched
to accordion. Shortly after, [Dutch popular singer] Willy Alberty paved
his way to a musical carreer by putting him in the spotlight during
concerts as 'the wonder boy on the squeezebox'.
Afterwards, Mooten played at various radio orchestras, and
effortlessly he switched to television. He became well known from his
appearances with Harry Bannink. In later years, with his ensemble
he accompanied Jasperina the Jong in the theatre.
All those years, he combined the serious work with gigs in the
commercial circuit. 'I am at home both at weddings and in the
Concertgebouw [Amsterdam's main classical concert hall]'.
In later years, Mooten found a new audience. For the youth,
he became known as 'de Grote Grijze Geitenbreier' [the Great Greay
Goat knitter], the musical right hand of Edwin Rutten in
the children's TV series 'de film van Ome Willem' [the movie of
Uncle William].
==========================
Two thoughts... That is the kind of man that should have found someone to mentor, to continue his legacy, perhaps taught a little at a conservatory. Kind of what Joe Macerollo is doing with Michael Bridge. I feel that no matter what the reason, illness, drinking, smoking, he passed too early and had so much to give. Also, wow, not bad for a self-taught man, that's the highest level I have personally seen anyone reach without "professional assistance".
This seems to be a repetitive story in many genres where talent, skill, ability and popularity lay strong in a person.