Syncopation is an accenting behavior that originates from feeling a polyrhythm (polypulse). A polyrhythm occurs when both pulses are actually played. For instance a dotted quarter note pulse originates 2:3 polyrhythm in a 3/4 bar. Feeling the dotted quarter pulse will cause melodies being played or sung to line up with upbeats of the quarter note pulse. The same principle goes for 4:3 polyrhythm to feel a dotted eighth note pulse, causing a behavior of syncopation when playing or singing melodies lining up with the "weak "beats of second and fourth sixteenth notes within a quarter note pulse.
Edit: yes, it requires you to feel 2 constant pulses at the same time. Syncopation is a rhythm feeling, where the lining up of 2 or more pulses causes the accents of one pulse to line up with the subdivisions of another. All syncopation is derived from a rhythm matrix, which is mostly absent in european classical music, but very common in African and Eastern traditions. It's the rhythm matrix lining up of 2 or more pulses that results in a "danceable feel". Most conservative definitions of syncopation just define syncopation as accenting weak beats, but that's missing the point altogether. It's probably from a western scholar perspective of feeling just the main pulse and mathematically observing seemingly random or odd accents, but that's a cause of syncopation, and not what it is. A common example is the stressing of the AND( upbeat) but that's just a result of a 2:3 polyrhythm being felt. A practical experiment can be done like this: clapping dotted eighths while tapping the foot to the main quarter note pulse, (2:3 polyrhythm) and singing an improvised Melody. It will be naturally syncopated. Once the secondary pulse is felt internally, there's no need to keep clapping, and the singing will always have the syncopated feel.
