TSRWFR 1
 For every time-span T there is an event e (or a 
 sequence of events e1e2) that is the head of T.

 TSRWFR 2
 If T does not contain any other time-span (that is, that 
 T is at the smallest level of time-spans), then e is 
 whatever event occurs in T.

 TSRWFR 3
 If T contains other time-spans, let T1,...,Tn be the 
 (regular or augmented) time-spans immediately 
 contained in T and let e1,...,en be their respective 
 heads. Then:
 a. (Ordinary Reduction) The head of T may be one 
  of the events e1,...,en.
 b. (Fusion) If e1,...,en are not seperated by a group 
  boundary ("locality" condition), the head of T may 
  be the superimposition of two or more of e1,...,en.
c. (Transformation) If e1,...,en are not seperated by
  a group boundary, the head of T may be some 
  mutually consonant combination of pitches 
  chosen out of e1,...en. *
 d. (Cadential Retention) The head of T may be a 
  cadence whose final is en (the head of Tn - the 
  last time-span immediately contained in T) and
  whose penult, if there is one, is the head of a 
  time-span immediately preceding Tn, though not 
  necessarily at the same level. *

 TSRWFR 4
 If a two-element cadence is directly subordinate to a 
 head e of a time-span T, the final is directly subordi-
 nate to e and the penult is directly subordinate to the 
 final.

 TSRPR 1 (Metrical Position)
 Of the possible choices for head of a time-span T, 
 prefer a choice that is in a relatively strong metrical 
 position.

 TSRPR 2 (Local Harmony)
 Or the possible chices for head of a time-span T, 
 prefer a choice that is 
 a. relatively intrinsically consonant,
 b. relatively closely related to the local tonic.

 TSRPR 3 (Registral Extremes)
 Or the possible choices for head of a time-span T, 
 weakly prefer a choice that has
 a. a higher melodic pitch
 b. a lower bass pitch

 TSRPR 4 (Parallelism)
 If two or more time-spans can be construed as 
 motivically and/or rhythmically parallel, preferably
 assign them parallel heads.