The years 1756 and 1828 embrace the life of J B Kleczyński, a distinguished Polish violinist, conductor and composer. His op. 4 collection is made up of six String Trios. Although Kleczyński employs the classical sonata cycle in all of them, his keen melodic sense makes the compositions original and full of interesting, fresh ideas rather than mere constituents of a wider whole. Listening and analysing them in their chronological order makes it possible for us to pick up the changes that occurred in Kleczyński's style, taking us from the rococo pastorality to the sophistication of classical means, or even a certain turn towards Romanticism. The String Trios op. 4 may be a grateful material for the modern recipient, being wonderful evidence that the music of the Classical era is much more than just Haydn, Mozart and Beethoven: there are plentiful musical gems by other masters too. A Pole, J B Kleczyński was one of such masters!