add dataset desc.

README.md

@@ -30,3 +30,16 @@ configs:
   - split: test
     path: data/test-*
 ---
+# Beijing Opera Instrument Classification
+This dataset is a collection of audio examples of individual strokes spanning the four percussion instrument classes used in Beijing Opera (Jingju, 京劇).
+There are four Beijing Opera instrument classes:
+
+Bangu (Clapper-drum) consisting of Ban (the clapper, a wooden board-­shaped instrument) + danpigu (a wooden drum struck by two wooden sticks)
+Naobo (Cymbals) consisting of two cymbal instruments Qibo+Danao
+Daluo: Large gong
+Xiaoluo: Small gong
+
+The dataset is adapted from [dataset link](https://compmusic.upf.edu/bo-perc-dataset).
+
+## Reference
+[1] Mi Tian, Ajay Srinivasamurthy, Mark Sandler, and Xavier Serra, "A Study of Instrument-wise Onset Detection in Beijing Opera Percussion Ensembles", in Proceedings of ICASSP 2014, Florence, Italy, May 2014.