Accents of Sanskrit, signs of change?

[Madhav Deshpande]

Dear colleagues,
 
         I am wondering if there are signs of change in the nature of Sanskrit accent in the following way.  Alternations like asti versus santi, and naumi versus nuva.h are linked to shifts of accent from the root to the suffix.  If these sorts of shifts indicate that an unstressed vowel gets contracted, or at worst deleted, can one infer that the accent of Sanskrit in its formative stages was stress accent, rather than pitch accent as it get represented in Vedic traditions?  Would pitch accent cause the same sort of contractions of vowels?  My second question is this.  While the correlation of vowel contractions with accent shifts is visible in verb forms and certain nominal paradigms, why is it that there is no similar effect left in the formation of Sanskrit compounds?  Consider the accent difference between a Tatpuru.sa versus a Bahuvriihi.  There are no vowel alternations similar to naumi versus nuva.h between Tatpuru.sa and Bahuvriihi.  Is it likely that the nature of accent changed from the stage when forms like naumi/nuva.h originated to the stage when compounds emerged?  Some food for thought.
 
                                                                                           Madhav Deshpande