Abstract: The task of isolating a target singing voice in music videos has useful applications. In this work, we explore the single-channel singing voice separation problem from a multimodal perspective, by jointly learning from audio and visual modalities. To do so, we present Acappella, a dataset spanning around 46 hours of a cappella solo singing videos sourced from YouTube. We also propose an audio-visual convolutional network based on graphs which achieves state-of-the-art singing voice separation results on our dataset and compare it against its audio-only counterpart, U-Net, and a state-of-the-art audiovisual speech separation model. We evaluate the models in the following challenging setups: i) presence of overlapping voices in the audio mixtures, ii) the target voice set to lower volume levels in the mix, and iii) combination of i) and ii). The third one being the most challenging evaluation setup. We demonstrate that our model outperforms the baseline models in the singing voice separation task in the most challenging evaluation setup. The code, the pre-trained models, and the dataset are publicly available at https://ipcv.github.io/Acappella/