1. A method of adjusting model parameters in a speech recognition system comprising: in a speech recognition system executed by computer system that combines recognition outputs from a plurality of parallel speech recognition processes that operate on a given speech input word sequence and produce different competing recognition outputs which are then combined to determine a final recognition output; wherein the speech recognition processes are complementary so as to produce different recognition errors on a given same speech input; performing a discriminative adjustment process including: i. selecting at least one acoustic model of the system, and ii. adjusting a plurality of model parameters of the selected acoustic model based on a joint discriminative criterion over a plurality of complementary acoustic models to lower combined recognition WER in the system over only independently discriminatively trained recognition systems.