You cannot activate "Urgent Tuning" while "Discord" is active because it lets you perform a Synchro Summon.
If "Discord" is Chained to the activation of "Urgent Tuning" the effect of "Urgent Tuning" is not applied and no monsters are sent to the GY.
Sending this card to the GY during your 3 End Phase after activation does not start a Chain.
You can activate the effect of "Blackwing – Vayu the Emblem of Honor" while "Discord" is active to Special Summon a Synchro Monster because it is not a Synchro Summon.
You cannot activate "Urgent Tuning" while "Discord" is active because it lets you perform a Synchro Summon. If "Discord" is Chained to the activation of "Urgent Tuning" the effect of "Urgent Tuning" is not applied and no monsters are sent to the GY.