______         __________        ______________
/      \       /          \      /              \
>     .         >      .          >>  .
| q q ; q q |,  | q q q; q q q |, | q q q q; q q q q |,  etc.
\_/
>

An indication of this process of differentiation into major and minor phases appears in the form of rhythm groups containing upwards of four elements.  In these the tendency is, as one observer expresses it, ’to consider the first two beats as a group by themselves, with the others trailing off in a monotonous row behind.’  As the series of elements thus bound up as a unit is extended, the number of beats which are crowded into the primary subgroup also increases.  When the attempt was made to unite eleven or twelve reactions in a single group, the first four beats were thus taken together, with the rest trailing off as before.  It is evident that the lowest groups with which attention concerned itself here were composed of four beats, and that the actual form of the (nominally) unitary series of eleven beats was as follows: 

_______________________
/                       \
>>        >        >
| q q q q; q q q q; q q q q |.
.        .        .

The subscripts are added in the notation given above because it is to be doubted if a strictly simple four-beat rhythm is ever met with.  Of the four types producible in such rhythm forms by variation in the accentual position, three have been found, in the course of the present investigation, to present a fundamental dichotomy into units of two beats.  Only one, that characterized by secondary accentuation, has no such discriminable quality of phases.  Of this form two things are to be noted:  first, that it is unstable and tends constantly to revert to that with initial stress, with consequent appearance of secondary accentuation; and second, that as a permanent form it presents the relations of a triple rhythm with a grace note prefixed.

The presence of this tendency to break up the four-rhythm into subgroups of two beats explains a variety of peculiarities in the records of this investigation.  The four-beat rhythm with final accent is found most pleasant at the close of a rhythmical sequence.  The possibility of including it in a continuous series depends on having the final interval of ‘just the right length.’  If one keeps in mind that a secondary initial accent characterizes this rhythm form, the value required in this final interval is explained by the resolution of the whole group into two units of three beats each, the latter of the two being syncopated.  The pause is of ‘just the right length’ when it is functionally equal to two unaccented elements with their succeeding intervals, as follows:  | .q. q q; .q % % |.

Likewise in four-rhythms characterized by initial stress there appears a tendency to accent the final beat of the group, as well as that to accent the third.  Such a series of four may therefore break up in either of two ways, into | >q. q; .q q | on a basis of two-beat units, or into | .q. q q; >q % %| on a basis of three-beat units.