Timepiece movement or watch including one isochronous oscillator mechanism, including only a first sprung balance oscillator including a first balance spring attached to a fixed structure at a first stud and to a first mobile component pivoting about a first axis, and a second sprung balance oscillator including a second balance spring fixed to a second mobile component, coupled to each other by mechanical connection via this second elastic return means attached to the first mobile component, this second balance spring being attached, to a felloe or an arm of the first mobile component at a second stud, and to this second mobile component which pivots about a second axis, and the maintenance of the oscillations is effected on only one of first mobile component or second mobile component.