One aspect of human existence that I find particularly valuable is that of creativity, and to be more specific, musicality. While not a uniquely human trait, I personally find music to be a core part of the human experience, and as such, I believe that there is value in exploring how a machine or other artificial creature could express this.
Mechanical Instruments:
Although we've had self-playing musical instruments for a long time now, I would argue that the more contemporary approach of repurposing electronic hardware to create a self-playing instrument is much more interesting when discussing how we can make an artificial musician. While a music box or mechanical organ replicate timbres we're already familiar with in a musical context, floppy disk drives and stepper motors were not designed with musical applications in mind. It would then arguably follow that the approach of using these unorthodox components as the voice for a mechanical instrument comes much closer to the likely origins of human musicality than a music box could ever dream of reaching. I say this because, for example, when a person sings, although they are making use of the biological systems granted to them, the primary "intended" function of their vocal chords is not to create music. Thus, the timbre of the human voice as a musical instrument is not the result of a conscious effort to create an instrument that sounds a particular way, but instead the result of using a preexisting biological system in a way it was not explicitly designed to. In much the same way, by creating an instrument out of repurposed hardware, you take a preexisting electromechanical system and use its timbral qualities to create something that had never been an intended feature of the system's design.
Imagining a Creature:
Now that we have a foundation for how our artificial musician might be able to interestingly produce its sounds, namely by finding some electromechanical hardware to repurpose, we need to imagine how this creature might be able to create music rather than just play it. As I believe that a significant part of musicality lies in the ability to play off of other musicians, I think that this creature should be able to take some musical input, analyze it and output a fitting continuation to what was played. In order to do this, the creature could have a MIDI keyboard attached to it to allow a person to play a short melody for the creature. From there, it could inspect the notes played and map the pitch and rhythm to whatever key, tempo and time signature the played melody is most likely to be (though the quality of this would be heavily dependent on the length and adherence to music theory best practices). Once the creature is "aware" of the relevant musical characteristics, potentially even factoring melodic and rhythmic motifs, it could try to use the information it has to continue off of the melody it was played, mimicking the interplay between human musicians.