A cellular musical composition method comprising: at a first apparatus: receiving a request for a cellular composition; receiving user data from at least one sensor, wherein the user data comprises data about the user and/or data related to the conditions under which the request is received; transmitting, to a second apparatus, a control signal comprising the request for a cellular composition and user data; at a second apparatus: receiving the control signal comprising the request and user data; filtering, using the received user data, at least one dataset containing a plurality of modules, each module comprising a plurality of cells, wherein each cell is an item of music; selecting responsive to the received user data, at least one cell from the filtered at least one dataset; arranging, responsive to the control signal, the at least one cell according to a pathway, wherein the pathway indicates the progression from one cell to another cell in the cellular composition; characterised in, at the first apparatus: receiving at least one change in user data; and determining, for each change in user data, a change type and a change magnitude, the change magnitude being determined by comparing the received change in user data with previous user data; generating a modified control signal comprising each determined change type and change magnitude; transmitting the modified control signal; at the second apparatus: receiving the modified control signal; identifying at least one transition rule corresponding to each determined change type and change magnitude, wherein the transition rule defines how to modify the cellular composition in response to the change in user data; and applying the at least one transition rule to the cellular composition. at a first apparatus: receiving a request for a cellular composition; receiving user data from at least one sensor, wherein the user data comprises data about the user and/or data related to the conditions under which the request is received; transmitting, to a second apparatus, a control signal comprising the request for a cellular composition and user data; receiving a request for a cellular composition; receiving user data from at least one sensor, wherein the user data comprises data about the user and/or data related to the conditions under which the request is received; transmitting, to a second apparatus, a control signal comprising the request for a cellular composition and user data; at a second apparatus: receiving the control signal comprising the request and user data; filtering, using the received user data, at least one dataset containing a plurality of modules, each module comprising a plurality of cells, wherein each cell is an item of music; selecting responsive to the received user data, at least one cell from the filtered at least one dataset; arranging, responsive to the control signal, the at least one cell according to a pathway, wherein the pathway indicates the progression from one cell to another cell in the cellular composition; characterised in, at the first apparatus: receiving at least one change in user data; and determining, for each change in user data, a change type and a change magnitude, the change magnitude being determined by comparing the received change in user data with previous user data; generating a modified control signal comprising each determined change type and change magnitude; transmitting the modified control signal; receiving the control signal comprising the request and user data; filtering, using the received user data, at least one dataset containing a plurality of modules, each module comprising a plurality of cells, wherein each cell is an item of music; selecting responsive to the received user data, at least one cell from the filtered at least one dataset; arranging, responsive to the control signal, the at least one cell according to a pathway, wherein the pathway indicates the progression from one cell to another cell in the cellular composition; characterised in, at the first apparatus: receiving at least one change in user data; and determining, for each change in user data, a change type and a change magnitude, the change magnitude being determined by comparing the received change in user data with previous user data; generating a modified control signal comprising each determined change type and change magnitude; transmitting the modified control signal; receiving at least one change in user data; and determining, for each change in user data, a change type and a change magnitude, the change magnitude being determined by comparing the received change in user data with previous user data; generating a modified control signal comprising each determined change type and change magnitude; transmitting the modified control signal; at the second apparatus: receiving the modified control signal; identifying at least one transition rule corresponding to each determined change type and change magnitude, wherein the transition rule defines how to modify the cellular composition in response to the change in user data; and applying the at least one transition rule to the cellular composition. receiving the modified control signal; identifying at least one transition rule corresponding to each determined change type and change magnitude, wherein the transition rule defines how to modify the cellular composition in response to the change in user data; and applying the at least one transition rule to the cellular composition.