ClassPass wants give users a way to work out even when they can't make it to a class.

The start-up best known for its fitness class subscription service is launching a free app loaded with audio workout tracks. Called ClassPass Go, it's ClassPass' latest attempt to diversify its business and expand its reach beyond the cities it operates in.

With the audio app, people will ideally be able to access workouts wherever they are — even if that means they're in a market where ClassPass isn't available. Yet it also means ClassPass will enter an increasingly crowded space with both start-ups like Aaptiv and established names like Peloton.

"We want this to be a product that's not just being used in big cities but also smaller towns and even globally," said ClassPass Senior Product Manager Dhaval Chadha.

ClassPass Go will initially feature cardio options — both indoor equipment such as the elliptical and outdoor options such as running and walking — high-intensity interval training, strength, yoga and meditation, Chadha said. ClassPass trainers will talk users through the moves, similar to other audio fitness apps.

Earlier this year, ClassPass introduced a video product called ClassPass Live. Subscribers receive a heart-rate monitor and a Google Chromecast so they can stream live classes or follow a pre-recorded session on their television.