Are you
Recycling
My song is a chorus of ringing instruments.
Machinery working
People with very dark titles employ my services.
Not sure - will amend in a later edit
The tough and rigid are brought before me.
Tough metals and plastics.
I see them weakened, deformed, drowned,
Beaten and shattered against each other
Break them apart
Until they can serve more practical means.
Make new objects
One of the elements gives me power,
Is this Carbon? Plastics are made from it.
We begin the same way.
Materials begin as plastic, and change to different forms.
My heart is a tragic lover,
And I close with a lonely reply.
This could possibly refer to the destruction of the earth, that recycling can help prevent.
Alongside another, I cause a memory to fade.
Forgetting old objects that have been thrown away?
With two others, I am a false imitation,
Some people think recycled products are inferior?
And I could allow a fraud to steal another's hand.
Recycling Fraud
Yet between honest folk, I enhance their trust.
Recycling can encourage communities to work together to help the enviroment?
There are quite a few unknowns, and this seems pretty unlikely, but I will try to fill in the blanks!