..for me was Jan Dismas Zelenka, a Czech Baroque composer.
I won't burden you with too much detail, if you are interested to learn more I can recommend this absolutely first class website, but suffice it to say that his music equals that of Bach, Handel and Vivaldi in its beauty and arguably occasionally exceeds them in its inventiveness. That Zelenka should remain so relatively unknown can only be regarded as a historical injustice of epic proportions.
My acquanitance began with this disc:
..which I can't recommend highly enough. The music is absolutely delightful, the performance by Ensemble Inégal and the Prague Baroque Soloists under Adam Viktora inspired and the recording excellent. Five strutses straight off the bat!
On the strength of this I have ordered a bunch more Zelenka discs and will report back with my findings.