Bandwidth for a single tone
If I pushed my doorbell button I'd hear a tone coming from the thing that makes the sound but that sound is not coming from the doorbell switch - it's on-off dc coming from the doorbell switch (because it takes two batteries to power it). The tone is created inside the wall thing - it recognizes the doorbell switch and activates an oscillator that sounds.

Similarly CW morse code works with a carrier that is turned on and off by the switch - the carrier is not the tone you hear but the carrier is (or can be) used to gate a tone generator at the receiver - the carrier can also be used to create the tone more directly by mixing it (at the receiver) with a frequency of similar frequency - this creates a difference frequency that can be audible (even though both received carrier and local oscillator are not).

The bandwidth of the channel therefore only needs to be a few hertz - enough to be able to recognize a dot from a dash at high transmission speed. However, if your morse code modulator is a bit crap it may generate a much wider bandwidth that can interfere with other stuff tuned close by.