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Setting  , we have defined the required affine map  with  This is the typical example to be memorized in the following abstract discussion of a stemma. Let
   , we use the field of its mother  , we first restrict that field to any of its daughters  and get the fields  . These sister fields to daughter  are then deformed under the endomorphisms  induced by the system parameters  . These deformed fields are then transported to  and weighted by the factors  . These sister fields influence the final value of the field at daughter  . Musically, this means that the performance at  is influenced by surrounding sister fields, which are typically the fields of past and future times (past or future periods, bars, etc.). Technically speaking, we proceed as follows: For each final vertex   the vertexes  lie in the set  . For the explicit calculation, we select a basis 
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be a mother. Then for each daughter 
, we define a triaffine (affine in each argument) map 
let 
be the ordered sequence of elements of 
. For the root 
and for each final vertex 
let us fix arbitrary 
, 
, respectively. The main task of 
of the vector space 
. This means that for every vertex 
we may consider the linear operators 
as a part of our data. Whence, if we identify 
with 
through the basis 
, we can define the homomorphism (1) as a triaffine map