Duo for Flutes in G major: Allegro and Minuet (1792)

Biamonti 32, WoO 26, Hess 17
If this score is any indication, Beethoven in Bonn was a nightowl. On the manuscript of this inventive and interesting duet, he dedicated to "friend Degenharth, 23 August 1792, 12 at night" (Contrarily, Biamonti feels that this notation doesn't fit Beethoven's character.) Later that year, Degenhart would return the favor later that year when Beethoven left for Vienna by assembling a farewell album for the young composer.
What is most interesting about this piece is the way that Beethoven is able to take the problem inherent in this ensemble: two flutes in basically the same register, and from this create an exciting and surprising sonata movement and minuet. Lively, cheerful, impressive. Degenhart must have been pleased. Recommended.

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YouTube is awash in performances, none really stand out, though here's a rather lively version.

Piano Trio in E flat major (1785-91)

Biamonti 31, WoO 38, Grove 153
Schindler says Beethoven wrote this when he was 15 (1785), mose scholars seem to dismiss this claim, accepting instead that it dates from 1791. Scholars debate whether this was intended to be a part of Opus 1, the set of Piano Trios. It does feature some firsts: Beethoven's first Scherzo, warm and gentle if overlong, and one of Beethoven's first codas at the end of a Sonata: a sonata which is charming and light, with a few treats, one being that very coda. The Rondo, an odd mixture of the brilliant and the lyrical - a la Mozart - has some interesting moments, particularly its ending. Throughout, there are few real melodies beyond the opening and the instruments seldom get the chance to shine: the work is piano-heavy. Beyond that, there also isn't the surety in switching from one topic to another that is a feature of Mozart or later Beethoven. Rather, one feels as if the work is awash in figuration, seeming like a minor work of Clementi, one lacking in excessive ornament. I like the piece, but I can understand how it could be frustrating.
Mislabelled as WoO 39 in the Brilliant Classics set.

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Ballet Music for Piano: "Ritterballet" (1790-1791)

Biamonti 30, Hess 89
A piano arrangement, presumably by Beethoven, of the Ritterballett (Biamonti 29) above. As one might expect, it works just fine on the piano.
Unheard Beethoven has created a midi version.

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Ballet Music: "Ritterballet", music for a ballet of knights (1790-1791)

Biamonti 29, WoO 1, Grove 149
The Ritterballet is graced with the distinction of being first among the unassigned, WoO 1 and has thus always held a strange fascination for me. In sound and in point it is an accomplished curiousity. Apparently, Beethoven was asked to create a ballet of sorts during which various regal aristocrats would traipse around in costumes while depicting important elements of the German aristocratic life such as hunting, drinking, dancing. With its initial performance for Count Waldstein on March 6, 1791, it became perhaps the only orchestral music of Beethoven heard in Bonn. The dances are generally pleasant and are linked by a recurring "German Dance."

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A portion of the Hunting Dance followed by the German Dance played as well as it may have been played in Bonn:

Aria in D major: "Mit Mädeln sich vertragen"; for bass & orchestra (c. 1790)

Biamonti 28, WoO 90
this second aria for bass and orchestra can actually be traced to the Geothe singspiel Claudine de Villabella in which it is sung antiphonally between Rugantino and the Vagabond chorus. The text of Beethoven's version is quite different from the version used by Reichardt. In Beethoven's version, the vagabonds have gone home, leaving a cheery bass to sing a rather solid Mozart buffa aria, compete with an onomatopoetic section based on the sound of swords clashing - kling, klang, ding, dang, and so forth. A real trick for a record needle test as it sounds very little like Beethoven.

Aria in F major: "Prüfung des Küssens"; for bass & orchestra "Meine weise Mutter spricht" (c. 1790)

Biamonti 28, WoO 89
Beethoven wrote two arias for bass ad orchestra using text from Goethe's singspiel Claudine de Villabella. The text itself was originally, it seems, part of a colaboration between Goethe and the famously pirckly composer Johann Friedrich Reichardt. Claudine itself is a work in the Sturm und Drang mode telling the story of the young Claudine and the awkward vagabond Don Pedro. Intrigue and disguises follow and eventually all end up happily ever after. A search of the libretto of the singspiel, however, does not turn up this text.

This singspiel aria for bass and orchestra gives us a sense of what Beethoven might have written if he were a completely different composer and writing buffa arias. It's a rather tame, Mozartian sentimentality buffa. Nothing gets out of control, nothing gets too exciting; the piece is over as it began.

Song in G major: "An Laura"; "Freud’ umblühe dich auf allen Wegen" (c. 1790)

Biamonti 27, WoO 112, Hess 128
Very CPE Bach, ABA: a sentimentality melody comprises the A section and an emotional outburst of recitative, the B. There is also a curious rangy piano interlude between sections. The original manuscript, discovered in 1911, was destroyed when someone, set off an incendiary device in the Beethoven-Haus in Bonn in 1960. Glauert (in the Cambridge companion to Beethoven) suggests that the melody strains against the vocal line - I would agree with this, I found it uncommonly difficult to work through.

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