There is provided an apparatus comprising at least one processing core, at least one memory including computer program code, at least one memory and the computer program code being configured to, with at least one processing core, cause the apparatus at least to obtain, from a first sequential input (102), a first output from a first recurrent neural network, the first sequential input being of a first modality, obtain, from a second sequential input (103), a second output from a second recurrent neural network, the second sequential input being of a second modality, and process the first output and the second output to obtain a correlation of the first and second sequential inputs.