Walls and Ceilings - [j]-patching Interior of exterior brick wall

I live in Pa and bought an old row house. My front cold wall is brick and I want to close it in and sound proof it. Right now, after tearing the paneling off, it's patchy old horse hair plaster and exposed areas of the actual front brick wall. I can even see light in areas. My approach is to first use concrete to seal the inside of the brick wall and even the missing plaster areas out with the plastered areas.

?? What type of concrete should I buy?
?? And is that the proper approach?

[j]

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