An apparatus to synthesize reference signatures , the apparatus comprising: memory; and at least one processor to execute computer readable instructions to at least: access a first sequence of media signatures collected from a first device , the first sequence of media signatures representative of a first portion of first media , ones of the first sequence of media signatures having corresponding first timestamps; identify and discard a first subset of the first sequence of media signatures associated with an event identified in metadata associated with the first sequence of media signatures, the event corresponding to a usage behavior and/or browser/player behavior to cause a discrepancy between at least one reference media signature representing the first media and the first sequence of media signatures ; change the first timestamps of ones of a second subset of the first sequence of media signatures that remain after the first subset is discarded to determine a modified first sequence of media signatures, so the timestamps assigned to the modified first sequence of media signatures are contiguous from before; and combine the modified first sequence of media signatures with a second sequence of media signatures collected from a second device different from the first device to form a sequence of reference signatures that represent the first media . memory; and at least one processor to execute computer readable instructions to at least: access a first sequence of media signatures collected from a first device , the first sequence of media signatures representative of a first portion of first media , ones of the first sequence of media signatures having corresponding first timestamps; identify and discard a first subset of the first sequence of media signatures associated with an event identified in metadata associated with the first sequence of media signatures, the event corresponding to a usage behavior and/or browser/player behavior to cause a discrepancy between at least one reference media signature representing the first media and the first sequence of media signatures ; change the first timestamps of ones of a second subset of the first sequence of media signatures that remain after the first subset is discarded to determine a modified first sequence of media signatures, so the timestamps assigned to the modified first sequence of media signatures are contiguous from before; and combine the modified first sequence of media signatures with a second sequence of media signatures collected from a second device different from the first device to form a sequence of reference signatures that represent the first media . access a first sequence of media signatures collected from a first device , the first sequence of media signatures representative of a first portion of first media , ones of the first sequence of media signatures having corresponding first timestamps; identify and discard a first subset of the first sequence of media signatures associated with an event identified in metadata associated with the first sequence of media signatures, the event corresponding to a usage behavior and/or browser/player behavior to cause a discrepancy between at least one reference media signature representing the first media and the first sequence of media signatures ; change the first timestamps of ones of a second subset of the first sequence of media signatures that remain after the first subset is discarded to determine a modified first sequence of media signatures, so the timestamps assigned to the modified first sequence of media signatures are contiguous from before; and combine the modified first sequence of media signatures with a second sequence of media signatures collected from a second device different from the first device to form a sequence of reference signatures that represent the first media . <EOS>