What is defined as a behavior or set of behaviors that can be measured and attained by working toward therapeutic goals?

The correct choice is target behavior, which refers to a specific behavior or set of behaviors identified for intervention in music therapy. Target behaviors are crucial in setting measurable therapeutic goals, as they are the focal points that therapists work towards modifying or enhancing through targeted interventions.

In music therapy, the identification of target behaviors allows practitioners to objectively assess progress and effectiveness. This sets a clear baseline and provides a structure for evaluating the client's development within the therapy process. By focusing on behaviors that can be directly observed and quantified, therapists can make informed decisions about treatment adjustments as necessary.

The other options, while related to the field, serve different purposes. Outcome measures pertain to the assessment instruments or metrics used to evaluate the overall effectiveness of the therapy. Focus area might describe a broader topic within therapy, and response behavior is more about the client's reactions or responses during the therapeutic process rather than the specific behaviors targeted for change.