Example apparatus disclosed herein are to detect a first watermark embedded in an audio stream associated with media, the first watermark embedded and detected based on a first watermarking technique; and detect a second watermark embedded in the audio stream, the second watermark embedded and detected based on a second watermarking technique. Disclosed example apparatus are also to assign the first watermark to a first monitoring track and to a second monitoring track, the first monitoring track limited to watermarks embedded in the audio stream based on the first watermarking technique, the second monitoring track limited to watermarks embedded in the audio stream based on any of the first or second watermarking techniques; group the first and second watermarks to form a media detection event when the second watermark is assigned to the second monitoring track; and cause transmission of the media detection event to a data collection facility.