Hi Michael,
first of all you should download the manual and read about how the sound engine of the E4-series works and what EOS (= Emulator Operating System) is capable of.
With the standard E4-hardware you are not able to route an incoming audio signal through the z-plane filters in realtime.
Therefore you need an E4 Ultra including the RFX-32 card and a related analog or ADAT I/O expansion.
You can only record a sample, set up a preset where you have to assign the sample to a keyzone and modify the playback-parameter (AMP, Filter, LFO, etc.) of the keyzone.
You should definetly use a mass storage media like an internal HD for storing your sounds.
If you don't read the word ULTRA on the front panel then you can only use SCSI HDs or purchase a card reader from
http://www.SCSIforSamplers.com, if available, and use CF-cards as discs.
Cheers,
Robert