Vs 1, 2

I will sing for my beloved
   my love-song about his vineyard:
My beloved had a vineyard
   high up on a fertile hillside.
   He trenched it and cleared it of stones
   and planted it with red vines;
he built a watch-tower in the middle
and then hewed out a wine-press in it.
He looked for it to yield grapes,
   but it yielded wild grapes.

The setting of this chapter of Isaiah was probably during the grape harvest, a famous time for converstaion and conviviality.  Isaiah uses a short parable to rouse his friends' consciences, and then with mounting vehemence attacks certain sins directly. (Howard Peskett, Isaiah - Trusting God in Troubled Times.  Lifeguide Bible Study. Introduction to Study 3.)

Isaiah the poet/prophet uses a 'love song' format to catch the interest of his listeners and get their minds working.

Vs 3,4

Now you who live in Jerusalem,
   and you men of Judah,
judge between me and my vineyard.
What more could have been done for my vineyard
that I did not do in it?
Why, when I looked for it to yield grapes, did it yield wild grapes?

Isaiah sets his listeners a problem to think about - one that they may have experienced themselves. They would be sympathetic to the vineyard owner who had been so diligent in caring for his vineyard, only to reap a poor crop.
 

Vs 5,6.

   Now listen while I tell you
   what I will do to my vineyard:
I will take away its fences and let it be burnt,
I will break down its walls and let it be trampled underfoot, and so I will leave it derelict;
   it shall be neither pruned nor hoed,
   but shall grow thorns and briars.
         Then I will command the clouds
   to send no more rain upon it.

I wonder if the listeners were by now beginning to suspect that Isaiah's story had another point to it?  Were they beginning to feel a bit uncomfortable?  Or were they still wrestling with the problem of what to do with the vineyard? some may have thought the vineyard owner was planning to do the right thing. Others may have thought the owner was a bit harsh.

V 7.

The vineyard of the Lord of Hosts is Israel,
   and the men of Judah are the plant he cherished.
He looked for justice and found it denied,
   for righteousness but heard cries of distress.

Now Isaiah hits them with the real message. His listeners - as we do too - must face the fact that God has showered his good gifts upon us and we do not use them to produce the 'fruit' he intended.  We turn a blind eye to injustice.  We get sucked in to the values of today's society.  We put other things in our lives before God.

So, what about the owner's plans? Now that we know Isaiah is talking about us, do we still agree that the owner's solution to his problem is the only practical one?  What if God gives up on us and leaves us to our own devices?   Praise him that he hasn't done that.  Instead, he has made a way for us to be forgiven and for us to be able to enter into a close parent/child  relationship with him through the sacrifice of Jesus on the cross.

There are puns used in the last two lines which would re-inforce Isaiah's message: the Hebrew words for justice and denied (NIV& NLT: bloodshed) sound similar, as do those for righteousness and cries of distress

New Bible Commentary, p 637.  Its double word-play defies reproduction, but might be freely rendered: 'Did he find right? Nothing but riot!  Did he find decency? Only despair.'  The parable brings home as nothing else could, the sheer unreason and indefensibility of sin - we find ourselves searching for some cause of the vine's failure, and there is none.  Only humans could be as capricious as that.