How did Music originate?

The view that music evolved from animal calls is psychologically implausible. I would suggest the evolutionary pathway is as follows.

The mechanism that permits human speech is a tiny bone called the hyoid, which anchors the glottis and makes its usage consistent and reliable for the vocal articulation, as opposed to mere vocalisation. Obviously human language evolved from similar survival requirements evident in other animal ‘languages’. But beyond this  an evolutionary byproduct of the earliest bicameral brain would have been the capacity to become aware of and articulate the reflexive sensations of pleasure /pain /attraction /disgust – which might be called proto-aesthetics.

I would hazard that the discovery of Song can be traced to enjoyment of the duality between the speech and calling - and the discovery that sustained vocalisation by its psychological nature induced a heightened awareness which, when used in a ’safe’ context, was amplified by listeners’ inner responses to the emotional vibrations (or intention) encoded onto it by the caller/singer.

Again, bicamerality has to lie behind the other major characteristic of Music: rhythm. No animals have access to continuous metricality, because it is an acquired skill wholly dependent on aesthetic discipline. Animals and children perform ‘musical’ actions by virtue of physical responses to brain impulses, and the nature of these impulses is conditioned by motor response (muscular energy) to the passing mental focus motivating it. It depends entirely on the evolution of bicamerality to be able to conceive of the existence of a right or wrong way of performing an action other than in terms of immediate pain or reward. And without that conception of a beat as existing abstractly from our own gesture/s, rhythmicality is impossible. I think one can see within the difference between single percussive sounds and sustained coherent rhythmic activity a very similar psychological mechanism unlocking the aesthetics of entertainment (or entrainment, if you will).
For further thoughts on the relationship between of timbre & consciousness

Many years ago, in VHS days, St Attenborough made a TV film exploring Animal ‘Music'. Essentially his conclusion, which I paraphrase, was that while animals make sounds for many purposes, there are no real examples in nature that would correspond to the self-reflexive intentionality which lies within human Music. (Well, some of it!)

Some animals, elephants for instance, can be trained to drum a beat just as they can be trained to paint pictures; but it is manifestly impossible for them to understand or attach emotional significance to actions which they would never have performed naturally - since the mental circuitry by which they could have invented them autonomously is not present within their limbic system.
We learnt from Blue Planet II this week that whales appear to be the only non-human species where sustained vocalisation (song) is shared equally between genders, and not an evolutionary trait of males. 

But there’s a further reason why birds or animals can’t be seen as the origins of music; and that is because if they were we’d still be doing it like them. Whereas the near-universal bedrock of evolved musical languages is a version of the stepped scale.