What I would do:
- Use a parametric notch EQ
- set the Q really high (60 or more)
- set the dB cut really low (-30 or more)
- tune it by ear to remove the hum frequency (which may not read exactly 60 Hz on your screen, because math and computers and analog are hard)
If you can do it on the stem (keyboard) then it’s unlikely this will have any phase problems with other bass sources (bass guitar, drums, etc.)
If you end up with phase problems, then you need to find a FIR/convolution plugin, which has all kinds of other problems, like needing delay compensation, which would make a dedicated hum remover a little more necessary, but I wouldn’t expect that problem to actually show up in practice.