Little River Band: ''The Net.'' (Capitol Records ST-12273) A constant visitor to the top-10 in American Pop/Rock, this band from Australia has consistently been a major musical force for the past eight years. Resting on its chart-busting laurels, Little River Band has remained relatively unchanged in its style and flavor - until now. With ''The Net,'' LRB's most diverse album yet , the band adds a new touch and new blood. ''The Net'' debuts Steve Housden on lead guitar and John Farnham as the new lead singer. With a versatile range, Farnham has brought a sterling quality to the vocals - they are more crisp and distinct than ever. A few hints of breaking into new styles is also present on the album. The best song of the record is the first cut, ''You're Driving Me Out of My Mind.'' Incorporating driving funk rhythms and some busy, exciting brass, the tune is lively and catchy. LRB never sounded like this before. Unfortunately, the album glides downhill from there. The numbers involve tight harmonies, a strength of LRB, but are repetitive and very predictable. Much of the blame rests on the drummer Derek Pellicci, who keeps simplistic, monotonous time. Yet LRB has taken a step for the better with ''The Net.'' The album shows a new musical competence of LRB to the skeptics, yet will not disappoint the many loyal fans of its consistently winning sound.