Last line in the chorus is "Anois ar theacht an tsamhraidh!"
"An samhradh" is, in this case, in the genitive.

Just wondering is it so because, in this case, "summer" is an indefinite quantity?

(I'm amazed at the rabbit hole of grammar I get into sometimes. When do I get any work done?...)
C.

teacht an tsamhraidh means "the coming of the summer". Tsamhraidh is pronounced taurig'. T'acht a taurig'
Ar theacht an tsamhraidh - at the coming of the summer. Er(') hacht a taurig'.

An samhradh is the nominative singular, not a form of the genitive. An tsamhraidh, as it appears in the lyric, is the genitive singular.



No, it's not to do with an indefinite quantity. It's the singular form of the noun "summer", meaning it has a fixed quantity of one.

The prefixing of the t is the result of using the definite article an in the genitive case with a 1st declension masculine noun beginning in s:

samhradh = summer
an samhradh = the summer
samhraidh = of summer
an tsamhraidh = of the summer

Check teanglann's grammar wizard if in doubt about these things. It's a good first port of call.