Q:

What are "tribal lays"?

There is a famous poem from Kipling: In the Neolithic Age.
There it says: 

"There are nine and sixty ways of constructing tribal lays, 
  "And every single one of them is right!"

My question
What are "tribal lays"? Is "lays" something like "laws", in the sense of "the way you organize society" (values, customs, culture etc.)?

A:

One distinct version of the noun lay has two definitions, according to Merriam-Webster's Eleventh Collegiate Dictionary (2003):

lay n {ME, fr AF lai} 1 : a simple narrative poem : BALLAD 2 : MELODY, SONG

In the context of "In the Neolithic Age," it seems likely to me that Kipling means "tribal lays" to refer to something like "essential songs or ballads of the tribe."
In his introduction to Rudyard Kipling, Stories and Poems (2015), Daniel Karlin has this to say about Kipling's reference to "tribal lays":

The problem we have with Kipling is partly of his own making. In his delightful skit about literary rivalry, 'In the Neolithic Age' [cross reference omitted], the lesson hammered home is that 'There are nine and sixty ways of constructing tribal lays | And-every-single-one-of-them-is-right'. Yet this easygoing principle depends on an unspoken agreement about what constitutes a 'tribal lay' and gives it value. The 'ways' of writing are not the same as its purposes, and Kipling eventually found himself engaging, with a will, in literary warfare for political or ideological ends. ... We are very far here from the aesthetic principle that all 'tribal lays' are of equal validity, and from the rollicking  depiction of disputes within a single literary tribe.

So Karlin thinks that "In the Neolithic Age" is a kind of satire of or commentary on the British literary scene of his own time, with tribal minstrels standing in for British men and women of letters, and with controversies over the proper direction of poetry and literature rendered as disputes over the proper way to construct a tribal lay.

A:

It might help to have some of the context from the Kipling poem In the Neolithic Age:

I was singer to my clan in that dim, red Dawn of Man,
  And I sang of all we fought and feared and felt.
  ...
  But a rival, of Solutré [a neolithic site in France], told the tribe my style was outré
   -- By a hammer, grooved of dolomite, he fell.
  And I left my views on Art, barbed and tanged below the heart
  Of a mammothistic etcher at Grenelle [a paleolithic site].
  Then I stripped them, scalp from skull, and my hunting-dogs fed full,
  And their teeth I threaded neatly on a thong;
  And I wiped my mouth and said, "It is well that they are dead,
  For I know my work is right and theirs was wrong."
  But my Totem [animal sacred to the poet's tribe] saw the shame; 
  from his ridgepole-shrine he came,
  And he told me in a vision of the night: --
  "There are nine and sixty ways of constructing tribal lays,
  "And every single one of them is right!"

The poet ("singer" to his clan) takes a stone ax (dolomite hammer) to a rival who dares criticize his style, shoots another rival artist, a cave painter, with an arrow ("barbed and tanged"), and goes on a general rampage against artists who disagree with him.  Eventually his tribal totem tells the poet in a vision that there are any number of right ways to construct the tribal narratives (i.e., the tribal lays).
A bit late for the Stone Age artistic community that the narrator has laid waste to.

A:

He is talking about the poet's craft.

Lay (n):
  1. A narrative poem, such as one sung by medieval minstrels; a ballad.
  2. A song; a tune. (Free Dictionary)

