O-methyltransferase that catalyzes the conversion of demethylmacrocin to macrocin, the penultimate step of tylosin antibiotic biosynthesis. Also able to mediate the conversion of demethyllactenocin to lactenocin. demethylmacrocin + S-adenosyl-L-methionine = H(+) + macrocin + S-adenosyl-L-homocysteine Optimum pH is 7.8-8.5. Antibiotic biosynthesis; tylosin biosynthesis. No production of demethylmacrocin.