Context: It appears that Horace mentions one after the other possible songs and singers to consider whether each is adequate to praise Caesar Augustus. In these lines he describe's Orpheus.unde vocalem temere insecutae
Orphea silvae,
arte materna rapidos morantem
fluminum lapsus celeresque ventos,
blandum et auritas fidibus canoris
ducere quercus.
I get a general idea of these lines: Orpheus's singing is so powerful that the woods followed along after him, while it holds back the tearing force of the rivers, and the swift winds; he coaxes the oaks who prick up their ears at his tuneful lyre.
Questions:
vocalem: is this to be taken substantively as the subject of the present participle morantem?
Orphea: how does this fit it? Does it agree with arte materna?
blandum: is this like vocalem to be taken substantively, as subject of the infinitive ducere?