Syrian Jews have a tradition of prolonging tarcha (tifcha) in certain verses, largely coinciding with those which Spanish and Portuguese Jews recite in High Na'um. For details, see the http://www.pizmonim.org website, under the tab "Torah readings".
Specimens of both may be found here. It is possible that the Mosul melody represents the older Iraqi tradition and that the Baghdad melody was imported from Syria following the appointment of Chief Rabbi Sadka Bekhor Hussein in 1743.