2. After logging in, click the "My" option at the bottom of the interface.
3. Click the "Settings" button in the upper left corner of the personal interface.
4. Select and click Help and Feedback.
5. Click "I want feedback" in this interface.
6. Click the "Please Select" button behind the feedback question type.
7. Click "Upload, Download and Missing Accompaniment".
8. Select "A cappella".
9. After choosing, fill in the accurate songs, and then click Submit Feedback.