Towards the end of the 15th century a style of polyphonic sacred music had been developed that can be heard in the masses of Johannes Ockeghem and Jacob Obrecht . Towards the end of the 15th century , polyphonic sacred music ( as exemplified in the masses of Johannes Ockeghem and Jacob Obrecht ) had once again become more complex , in a manner that can perhaps be seen as correlating to the stunning detail in the painting at the time .