Simple average labour, it is true, varies in character in different countries and at different cultural epochs, but in a particular society it is given. More complex labour counts only as intensified, or rather multiplied simple labour, so that a smaller quantity of complex labour is considered equal to a larger quantity of simple labour. Experience shows that this reduction is constantly being made. A commodity may be the outcome of the most complicated labour, but through its value it is posited as equal to the product of simple labour, hence it represents only a specific quantity of simple labour.15 The various proportions in which different kinds of labour are reduced to simple labour as their unit of measurement are established by a social process that goes on behind the backs of the producers; these proportions therefore appear to the producers to have been handed down by tradition. In the interests of simplification, we shall henceforth view every form of labour-power directly as simple labour-power; by this we shall simply be saving ourselves the trouble of making the reduction. p. 135

Is intensified/multiplied labor referring to the use of fixed capital in production? I.e. the machinery as dead-labor whose value is then transferred to the product through living labor, intensifying the value transferred into a commodity per unit of labor-time? Or to forms of labor which are more difficult/intensive/complex?

If the latter, is Marx always considering that 1 hour = 1 hour? I understand how this works in the abstract, but I guess I am just curious how this has implications for the later imagined association of "free men" (though perhaps I am subjecting his "parallel" to too much scrutiny):

We shall assume, but only for the sake of a parallel with the production of commodities, that the share of each individual producer in the means of subsistence is determined by his labour-time. Labour-time would in that case play a double part. Its apportionment in accordance with a definite social plan maintains the correct proportion between the different functions of labour and the various needs of the associations. On the other hand, labour-time also serves as a measure of the part taken by each individual in the common labour, and of his share in the part of the total product destined for individual consumption. p 172

Both quotes from the Fowkes translation.