Thanks to the help of several kind Listers, I've been able to put
together a story for my friend.  Though this certainly isn't complete,
nor perhaps even precise in a musicological sense (though hopefully
accurate as far as it goes), I present it here for general consumption.

Question: What was the earliest piano concerto that was composed by a
woman?

Answer: After a little investigation, the answer probably is: no one
is sure.  There are several complicating factors.

First, the works of relatively obscure composers - and nearly all women
composers of previous centuries were obscure - are often difficult to
date accurately.  Particularly as we move back into the 18th century,
Even some works by major composers are difficult to date with any certainty
(in fact, in a few cases we don't even know the exact birth and death dates
of the composer in question).  We often must rely on the letters or diaries
of a composer to help date specific works.  The more obscure the composer,
the more likely it is that few of these writings still exist.

Second, there are generally no comprehensive references that list such
things.  To proceed one must make a list of possible candidates, and then
search their works lists to see if a concerto exists.  Coming up with a
comprehensive list of women composers is hard enough, and this is further
complicated by the general lack of rigorous scholarship into obscure
musical figures, meaning that works lists are often incomplete or just
plain wrong (sometimes actually misattributing works of lesser composers to
more famous figures, as was sometimes done in the past to try and stimulate
sales of scores).

Lastly, even the definition of "piano concerto" is up for grabs.  The first
keyboard concertos were written in the High Baroque period just after the
beginning of the 18th century.  At this time, the most common keyboard
instruments were the harpsichord (aka cembalo, clavecin, etc.), clavichord,
and organ.  The clavichord was too weak to use as a concertante instrument
(it was really meant for intimate performance), so most of the concertos
(ex., those of Handel and Bach) are written for either harpsichord or
organ, or the choice was left to the performer (Haydn's earliest concertos
are known for this).  Today, these concertos are sometimes performed on
modern piano. The middle of the 18th century was a time of tremendous
change in instrument design and construction.  The newfangled piano (often
referred to these days as a fortepiano; quite different in sound and size
from a modern piano) were becoming widely available, and composers were
starting to write concertos (and pieces such as solo sonatas and other
chamber works) for the sound of the new instrument.  Mozart's first four
or five concertos were probably written with the harpsichord in mind,
whereas his later (and more famous) concertos were definitely written for
the fortepiano. The piano as we know it began to emerge in the early to
middle part of the 19th century.  Beethoven (in say the 1810s and 1820s)
had access to the latest in piano technology, but even these instruments
sound considerably different from a modern Steinway, for example.  They
tended to be quieter and more subtle in soud, they had less range (fewer
keys), and they had a more delicate timbre with more complex sonorities.
Performances of Beethoven's piano works on period fortepianos are abundant
these days, for instance, but many people are initially put off by the
sound of a fortepiano. The most common complaint when comparing these
older instruments to modern version is that they sound thin and somewhat
like a toy or honky-tonk piano.

In addition to evolution of instruments in the 18th century, the makeup of
performing ensembles was changing rapidly as well.  Major orchestras, such
as the renown ensemble at the court of Mannheim in the 1730s, were getting
larger and incorporating as many as 40-50 players.  But at the same time,
the older Baroque orchestra (ex., for Bach's Brandenburg Concertos) was
often no more than a dozen strings augmented by a handful of wind players.

In any case, assuming a "piano concerto" is defined as a work for a
keyboard instrument (but not an organ) accompanied by a diverse ensemble
of musicians, here are some likely candidates:

Maria Theresia von Paradis or Paradies (1759-1824), a blind virtuoso
keyboardist and friend of Mozart's who wrote two piano concertos, but they
are apparently lost.  No dates for these works exist, but many of her other
works that can be dated are from the 1790s.

Anna Amalia (Duchess of Saxe-Weimar) (1739-1807) wrote a concerto for
12 instruments and cembalo obbligato (solo harpsichord), it is however
undated.  As mentioned above, these sorts of "chamber concertos" were
often the form concertos took in the early 18th century when "orchestras"
were often not more than 12-20 players.

Maria Hester Park (1760-1813) composed a piano concerto in E Flat Major
Op. 6.  Given the dating of her Op. 4 sonatas as 1790, I would assume
the concerto dates from before 1800.

Marienne Martinez (1744-1812) wrote two piano concertos and no dates are
given, but the earliest may date from about 1772.

Maria Magdalena Kauth (late 18th cent) wrote a concerto for piano &
orchestra dated as 1792.

Jeanne Cecile (18th cent) wrote a chamber concerto for piano, 2 violins, 2
oboes, 2 horns, viola & continuo dated as 1783.

It appears we have a few likely candidates, and there are undoubtedly a
host of others.  I think it's safe to say that the first piano concerto
written by a woman probably appeared in the period 1770-1800.  By way
of comparison, the very first piano concertos (not including strictly
harpsichord concertos) appeared circa 1767 by the likes of Mozart and Haydn
and the very first harpsichord concertos were probably by Bach, circa 1733;
intended as didactic vehicles for the musical instruction of his sons.

Dave
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