Interference of acoustic and convective disturbances controls the development of self-excited combustion oscillations of a lean-premixed swirl-stabilized flame with a central bluffbody. How this interference mechanism influences the dynamics of multiple interacting flames in a multi-nozzle environment is currently unknown. Here we present observations of a multi-nozzle system's response to staggered swirler arrangements (xi(sw.1)not equal xi(sw.2)) as compared to non-staggered arrangements; the distance between the swirler and the flame is the dominant length scale of vortical disturbances. Our results demonstrate that a slight modification of the swirler arrangement in the streamwise direction - staggered or nonstaggered - has a remarkable influence on the stability map of the whole combustion system. Phase-resolved flame imaging measurements indicate that under non-staggered conditions interacting swirl flames feature a coherent motion during a period of oscillation. By contrast, the staggered swirler combination creates significantly non-symmetric flame dynamics, disturbing the development of well-organized motion over the entire reaction zone. Flame surface modulations in the lateral direction are particularly pronounced due to the formation of non-symmetric convection delays of vortical disturbances between adjacent swirl nozzles. For a given swirler arrangement, the system's response to a wide range of combinations of mean nozzle velocities, including symmetric ((u) over bar (1) = (u) over bar (2)) and non-symmetric ((u) over bar (1) not equal (u) over bar (2)) conditions, were explored to account for the simultaneous effects of the two convection parameters. Our data show that a major determinant of the onset of the instability is the combination of the Strouhal numbers, < St(1), St(2)>, which can be even or uneven depending on the manipulation of the convection time of each nozzle. (C) 2018 The Combustion Institute. Published by Elsevier Inc. All rights reserved.