Original sentence - Peter Tchaikowsky, a Russian composer, lived from 1840 to 1893. He composed Peter and the Wolf.
Revision -Peter Tchaikowsky, a Russian composer who lived from 1840 to 1893, composed Peter and the wolf.
Should we set off 'a Russian composer' phrase from the rest of the sentence with pair of commas because it's appositive phrase?
Why we should use comma after 'who lived from 1840 to 1893 in the second sentence, and do we consider 'who' clause - sentence subject ?
What is 'composed Peter and the Wolf' on the second sentence - participle phrase or the verb and the object of the'who' clause and if not how is this phrase function in the second sentence?
It depends on if you are going for dramatics or contrasting expression. Think of commas as pauses, although pausing does not always work, in this case it does. Also, decide if the information is essential or non essential. You would use 2-commas to set off nonessential words and word groups example: The Dodge Caravan that is leaking break fluid is mine. = essential since if asked, which Dodge out of all others. Well, the one that is leaking break fluid. Next Dodge Caravans,which are roomy family vehicles, are spacious. = nonessential since we can take out(which are roomy family vehicles) and still complete the meaning. (Dodge Caravans are spacious.)
Here are a few comma rules not all but a few.
Most importantly think of the sentence structure that you are using is it a simple sentence, compound, complex, or compound-complex then recognizing the proper usage of a comma becomes "easy peesy"
Understand what a comma is - a punctuation mark that separates.
Use to separate a main clause from an introductory word or word groups.
To enclose or separate a nonessential word or groups that came within or after a main clause.
To separate two main clause, but do not forget the fan-boys or else you will have a run on or fused sentence.
Use commas to show series or a list
and in dates and addresses.
research the Oxford comma