The successful string-breaking model of particle production is extended in order to help explain the momentum distribution in elementary collisions. We examine the effects of fluctuations of the string on the observed thermal p(t) distribution. In particular, following a suggestion of Bialas, we allow the string tension to fluctuate and show how experimental data place constraints on the probability distribution of fluctuations. Consequences for the relative yields of light, strange and heavy quarks are explored.