We present how the open-source web framework Dezrann enables users to hear, study, and annotate music by interacting with synchronized views such as image scores, rendered scores, videos, and representations of audio as waveforms or spectrograms. We encode as unit conversions the cross-modal synchronization between these music representations. Composing these conversions allows us to conveniently translate musical time, audio time, and graphical positions, as well as to synchronize annotation labels across views. Uses of the Dezrann platform or of some of its components include corpus annotation for musicology or computer music research, music education, as well as collaborative score edition and correction in the CollabScore project.