If you want to apply some individual EQ or anything else to one note - it is possible without automation and all that tiresome stuff:
- Cut this one second from the audio event, creating it’s own event
- Select this new audio event
- in the upper tab go Audio=>Plug-Ins=> select your eq here. Cubase’s Studio EQ is good for that stuff since it has an analyzer
- when you see a plug-in interface, press “preview” below, and this audio will cycle playback
- find that frequency and notch it out
- crossfade this edited event with it’s neighbors (select all three and press X)
- this change is not permanent. You can go Audio=>Offline Process History and make changes to that EQ.
If you have to cut to much that this change catches the ear, layering some simple VSTi instrument below could work. Halion SE is enough for that, just lower the attack of the instrument since you just need it’s sustain to mask the EQ notch.
Melodyne and RX3 could do it better, of course, but still there are many things we guys on a budget can do with Cubase))