This is held true by the wise of Eressëa, that all those of the Quendi [Elves] who came into the hands of Melkor, ere Utumno was broken, were put there in prison, and by slow arts of cruelty were corrupted and enslaved; and thus did Melkor breed the hideous race of the Orcs in envy and mockery of the Elves, of whom they were afterwards the bitterest foes. For the Orcs had life and multiplied after the manner of the Children of Illúvatar; and naught that had life of its own, nor the semblance of life, could ever Melkor make since his rebellion in the Ainulindalë before the Beginning: so say the wise. And deep in their dark hearts the Orcs loathed the Master whom they served in fear, the maker only of their misery. This it may be was the vilest deed of Melkor, and the most hateful to Ilúvatar.The perversion of elves into Orcs is such a heinous act that JRR Tolkien wrote several times in letters that he wished he hadn't thought of it. The creation of Dwarves at Aulë's hand and Yavanna's leadership in creating the Ents (the only two thinking races not created by Iluvatar himself) is a beautiful and well-written chapter of the Silmarillion (whence all these quotes). How Orcs came to be only warrants a few sentences, clues and oblique stories of Melkor's typical stratagies of converting his foes to unwilling cohorts.
Now in his heart Melkor most hated the Eldar, both because they were fair and joyful and because in them he saw the reason for the arising of the Valar, and his own downfall. Therefore all the more did he feign love for them and seek their friendship, and he offered them the service of his lore and labour in any great deed that they would do. The Vanyar indeed held him in suspicion, for they dwelt in the light of the Trees and were content; and to the Teleri he gave small heed, thinking them of little worth, tools too weak for his designs.The elves who remained in Middle Earth were either Teleri who didn't have the gumption to complete the Great March or those Unwilling to start the march at all. Melkor, in this thought, does not even consider them worth a thought.... But
the Noldor took delight in the hidden knowledge that [Melkor] could reveal to them; and some hearkened to words that it would have been better for them never to have heard. Melkor indeed declared afterwards that Fëanor had learned much art from him in secret, and had been instructed by him in the greatest of all his works; but he lied in his lust and his envy, for none of the Eldalië ever hated Melkor more than Fëanor son of Finwë, who first named him Morgoth; and snared though he was in the webs of Melkor's malice against the Valar he held no converse with him and took no counsel from him.
Even so, Melkor's cunning was the downfall of the Noldor, and Fëanor, too.
Ever Melkor found some ears that would heed him, and some tongues that would enlarge what they had heard; and his lies passed from friend to friend, as secrets of which the knowledge proves the teller wise. Bitterly did the Noldor atone for the folly of their open ears in the days that followed after.
The lies told were many and subtle. They had the desired effect on the Noldor Elves
when Melkor saw that these lies were smouldering, and that pride and anger were awake among the Noldor, he spoke to them concerning weapons; and in that time the Noldor began the smithying of swords and axes and spears. Shields also they made displaying the tokens of many houses and kindreds that vied one with another; and these only they wore abroad, and of other weapons they did not speak, for each believed that he alone had received the warning.
Another similarity: Aulë forged dwarves in secret. Noldor forged swords in secret. Do any other Ainu or elves forge in secret, except for the Enemies?
And Fëanor made a secret forge, of which not even Melkor was aware; and there he tempered fell swords for himself and for his sons, and made tall helms with plumes of red. Bitterly did Mahtan rue the day when he taught to the husband of Nerdanel all the lore of metalwork that he had learned of Aulë.
As an Aulë-centric (forgive mixing Quenya and Latin) view, perhaps the Melkor's choice of the Noldor as the people to subvert was influenced by Melkor's deep hatred of Aulë and Aulë's weakness this ploy. The Vanyar, so treated, would have confided in Manwë. The omni-present Ulmo would have heard Melkor himself if he'd had sought the Teleri. It is the favorites of the distracted Vala Aulë that have to see through it for themselves.
The Elves fail at first, but learn. In example, Fëanor, believing Melkor's lies that the Vala were holding the elves as thralls, begins to harangue for sedition and escape, even becoming violent against his own half-brother Fingolfin in front of their father, Finwë.
Then there was great unrest in Tirion, and Finwë was troubled; and he summoned all his lords to council. But Fingolfin hastened to his halls and stood before him, saying: 'King and father, wilt thou not restrain the pride of our brother, CuruFinwë, who is called the Spirit of Fire, all too truly? By what right does he speak for all our people, as if he were King? Thou it was who long ago spoke before the Quendi, bidding them accept the summons of the Valar to Aman. Thou it was that led the Noldor upon the long road through the perils of Middle-earth to the light of Eldamar. If thou dost not now repent of it, two sons at least thou hast to honour thy words.'
But even as Fingolfin spoke, Fëanor strode into the chamber, and he was fully armed: his high helm upon his head, and at his side a mighty sword. 'So it is, even as I guessed,' he said. 'My half-brother would be before me with my father, in this as in all other matters.' Then turning upon Fingolfin he drew his sword, crying: 'Get thee gone, and take thy due place!'
Fingolfin bowed before Finwë, and without word or glance to Fëanor he went from the chamber. But Fëanor followed him, and at the door of the king's house he stayed him; and the point of his bright sword he set against Fingolfin's breast 'See, half-brother!' he said. 'This is sharper than thy tongue. Try but once more to usurp my place and the love of my father, and maybe it will rid the Noldor of one who seeks to be the master of thralls.'
This was the first use of a weapon. Ever. Fingolfin, displaying super-human restraint, was not attacked, but the mere threat was enough to bring Fëanor to trial by the Valar. There, Melkor's subterfuge is uncovered.
Fëanor standing before Mandos in the Ring of Doom was commanded to answer all that was asked of him. Then at last the root was laid bare, and the malice of Melkor revealed; and straightway Tulkas left the council to lay hands upon him and bring him again to judgement. But Fëanor was not held guiltless, for he it was that had broken the peace of Valinor and drawn his sword upon his kinsman; and Mandos said to him: 'Thou speakest of thraldom. If thraldom it be, thou canst not escape it; for Manwë is King of Arda, and not of Aman only. And this deed was unlawful, whether in Aman or not in Aman. Therefore this doom is now made: for twelve years thou shall leave Tirion where this threat was uttered. In that time take counsel with thyself, and remember who and what thou art. But after that time this matter shall be set in peace and held redressed, if others will release thee.'
Then Fingolfin said: 'I will release my brother.' But Fëanor spoke no word in answer, standing silent before the Valar. Then he turned and left the council, and departed from Valmar.
Thus, haughty and proud Fëanor is himself exiled from Tirion for 12 years with his sons. When Melkor appears to offer sympathy, Noldo Fëanor appears to have learned something:
Suddenly he [Melkor] came to Formenos, and spoke with Fëanor before his doors. Friendship he feigned with cunning argument, urging him to his former thought of flight from the trammels of the Valar; and he said: 'Behold the truth of all that I have spoken, and how thou art banished unjustly. But if the heart of Fëanor is yet free and bold as were his words in Tirion, then I will aid him, and bring him far from this narrow land. For am I not Vala also? Yea, and more than those who sit in pride in Valimar; and I have ever been a friend to the Noldor, most skilled and most valiant of the people of Arda.'...
Now Fëanor's heart was still bitter at his humiliation before Mandos, and he looked at Melkor in silence, pondering if indeed he might yet trust him so far as to aid him in his flight. And Melkor, seeing that Fëanor wavered, and knowing that the Silmarils held his heart in thrall, said at the last: 'Here is a strong place, and well guarded; but think not that the Silmarils will lie safe in any treasury within the realm of the Valar!'
But his cunning overreached his aim; his words touched too deep, and awoke a fire more fierce than he designed; and Fëanor looked upon Melkor with eyes that burned through his fair semblance and pierced the cloaks of his mind, perceiving there his fierce lust for the Silmarils. Then hate overcame Fëanor's fear, and he cursed Melkor and bade him be gone, saying: 'Get thee gone from my gate, thou jail-crow of Mandos!' And he shut the doors of his house in the face of the mightiest of all the dwellers in Eä.
Other Noldor immediately report this to Manwë (Not Aulë. Manwë) and Melkor eludes the Vala searching for him.
Verdict: The Noldor cannot unify against Melkor. Melkor effectively splits and removes them from almost all their allies, including Aulë. They they suffer even greater humiliations than the above at their own hands because of Melkor's believable insinuations.