1) The document discusses a semi-supervised nonnegative matrix factorization method with a cosine penalty condition for audio source separation. 2) It proposes adding a cosine similarity penalty term to penalize similarity between basis matrices, to improve on existing penalized SNMF methods. 3) Experiments show the proposed method achieves higher source separation performance compared to existing methods, measured by average and median SDR values, but the optimal weight coefficient values are peaky.