Redrum
To remove a sample from a Redrum drum machine, select its drum sound channel and then select "Delete Sample" from the Edit menu.
The sample is removed from the drum sound channel and from sample memory.
NN-I9
To remove a sample from an NN-19 Sampler's memory, select the zone it belongs to, and then select "Delete Sample" from the Edit menu.
The sample is removed from the zone and from sample memory.
NN-XT
To remove a sample from an NN-XT Sampler's memory, select the zone it belongs to, and then select "Remove Samples" from the Edit menu.
The sample is removed from the zone and from sample memory. The zone still remains though. To delete a zone, you must use the option "Delete Zones".