It’s not easy to learn.

1. Violin: The violin is the most difficult stringed instrument to learn among all musical instruments. The violin is known as the "Queen of Instruments", and its pitch, posture, and technique are all relatively difficult. Learning the violin requires perseverance.

2. Pipa: Pipa is the most difficult to learn among the national musical instruments. Pipa's ring fingering is the most difficult. It requires a long time of training before you can do it well. Learning pipa requires sufficient flexibility and strength in the hands.