Online music platforms, third-party tools, and web searches.

1. Online music platforms: Visit major online music platforms, such as NetEase Cloud Music, QQ Music, etc., search for the keyword "Erhu accompaniment" on the platform, and select suitable tracks to download. These platforms usually provide free or paid Erhu accompaniment libraries, and users can choose according to their personal needs.

2. Third-party tools: There are third-party tools or software that can be used to download the Erhu accompaniment library. For example, use an online music conversion tool to convert video or audio files to MP3 format, and then select the desired erhu accompaniment for download. In addition, some music editing software also provides downloading and editing functions of accompaniment libraries.

3. Internet search: Enter the keyword "erhu accompaniment download" or "erhu accompaniment library" in the search engine, browse the search results, and select the appropriate website or resource to download. When choosing download resources, you should ensure that the downloaded tracks are legal and compliant to avoid infringement issues.