Attentional bias modification (ABM) is cost-effective, accessible, and could meet the increasing demand for mental-health treatment. However, ABM paradigms that reliably modify attentional biases (AB) and symptoms are still required. Consequently, we examined the feasibility of a novel ABM intervention (gaze-contingent consonant and dissonant music heard when looking at positive and negative faces, respectively). Contingency awareness and use, and participant adherence and dropout assessed if the intervention could be done. Negative affect, state rumination, and negative AB (longer dwelling on sad and angry faces) after a single session (Study 1, N = 13), and negative affect, trait rumination, depression, anxiety, and negative AB after four sessions (Study 2, N = 10) assessed whether the intervention should continue. The intervention could be done as (1) the music versions and their contingency were discerned and deliberately controlled by some participants, and (2) the participants adhered to the study with no dropouts. Although reductions in positive affect were seen across the studies, the intervention should continue to be explored as on the whole, reduced negative affect (or no change), state and trait rumination, depression, anxiety, and baseline negative AB were found post-intervention in descriptive data. Clinically-relevant changes in rumination, depression, and anxiety scores were found for some participants. AB change (attenuation/reversal/increase) depended on the contrast (emotional-neutral and/or emotional-emotional). An evaluation of the studies showed that task instructions, music selection, and the number of sessions to be delivered requires further exploration. In conclusion, gaze-contingent music ABM is feasible and should be further explored to ensure it works as intended for a larger number of individuals. Encouragingly, clinically-relevant changes in rumination and symptom levels were reported after four sessions. The differing emotional-neutral/emotional-emotional results could underlay/contribute to the lack of AB change found in the commonly used emotional-neutral ABM literature. Thus, both contrasts should be assessed.