The Piano Trio Opus 1, No. 3, is Beethoven’s first major work in C minor. His fifth symphony is in C minor, as are the third piano concerto, the seventh violin sonata, the ‘Coriolan’ overture, the ‘funeral march’ of the Eroica symphony and his last piano sonata, Op. 111 – all works of a powerfully (and demonstratively) dramatic character. It is the key most associated with the mythic, dramatic, heroic Beethoven-persona. The piano-trio form, which had had a fairly polite history up to this point, might not seem an obvious point for C-minor Beethoven to have shown himself, but his voice and this dramatic mood is powerfully present, and perhaps this salon-music genre put the young composer into the sharpest relief. He brought a dark and stormy music (music of surprises, storms, and mysterious disappearance) into the salons and living rooms of Vienna, and set himself up as a composer with a strong voice and quite a bit of income.
Aside from the key, one might do well to consider for a moment the presence of variation form in the slow movement. Beethoven wrote many great sets of variations. The ‘Diabelli’ variations, the fifth movement of the C# minor String Quartet Op. 131, and the last movement of the Eroica symphony come to mind. Among these examples, the slow movement of the piano trio hardly stands out, but it does bring a particular Beethoven-quality to the fore: his ability to take something simple, something on the border (and sometimes over the border) of banality, to make it memorably dense or memorable, and then mine it until it reaches a kind of completeness and/or breaks down. He will give a theme so simple that a listener must ask ‘why?’ – and then he will give you more good reasons than you need. This is all to say, that the opus number fits. Not because the trio indicates what is to come from Beethoven, but because it shows a composer fully engaged with moods and forms which would deeply engage him for his entire oeuvre.