It is well known that Beethoven was a musical revolutionary. The size and loudness of his 3rd Symphony, "The Eroica", challenged the accepted musical conventions of his time and provided the foundations upon which later composers would build; the epic, all embracing symphonies of the Romantic and Late Romantic periods of music (epitomised by Bruckner and Mahler respectively) would not have been possible without the inspirational impetus provided by Beethoven.
But Beethoven was
also revolutionary in subtle and quiet ways.
For example, Beethoven would sometimes start his concertos (pieces for soloist and orchestra) quietly, introducing the soloist in an understated and reflective way: his 4th Piano Concerto begins quietly, introducing the soloist not with a virtuosic flourish but with a reflective prayerlike meditation.
This quietness broke the musical conventions of the time: most contemporaries of Beethoven
would start their concertos with a loud flourish and provide solo parts that were written to show off the brilliant virtuosic skills of the soloist.
The subtly revolutionary act of starting quietly immediately freed
the music from the shackles of virtuosic "display for display's sake" and enabled Beethoven to add emotional depth to his concertos,
elevating them to a place beside his symphonies in terms of their ability to express profound feelings.