First of all, we should learn the pronunciation characteristics of various musical instruments, and then consciously identify them during each listening. First concentrate on identifying the parts of musical instruments that have mastered the acoustic characteristics, and then listen repeatedly to increase the storage of acoustic impressions in the brain. Then, after gradually mastering the awareness of musical instrument acoustic characteristics, the composite acoustic effects of multi-voice, multi-level and multi-instrument are superimposed and identified, which increases the difficulty.

I recommend listening to the encyclopedic audio materials aimed at the characteristics of western musical instruments —— A Guide to Youth Symphony written by British composer Britten. It is easier to identify the characteristics of national musical instruments, because the acoustic effects of national musical instruments are exclusive and very independent, and it can be easily identified by listening to folk music ensembles or solo tracks.

In addition, there is a high similarity between cello and viola in western symphonies. Pay attention to experience identification, listen more, know more about music background and watch more videos to distinguish them.