Compression comes in many flavours. And most on multi-fx units are not that good.
There are a couple of pedal type compressors which do stand out..EBS, for one, but most are lacking in both control and sound.
Many "pro" compressors will run much $$ (My Avalon was in excess of 2 grand) but there are some very cool ones out there for less.
Do some research on compressors and find what you might be interestred in it for. Compression is an "effect" which, when used right, should not be discernable. Altho..as a caveat to that I will add that overt "pumping" compression can be a cool effect in electronica.
Some units worth researching:
The aforementioned EBS Multicomp
ART Levelar (very inexpensive, sounds really good on bass)
FMC RNC (Real Nice Compressor..1/2 rack size. very good)
Joe Meek (forgot the model #)
and..oddly enough.the photo/optic compressor on the Fishman Platinum Bass EQ/Preamp/DI is very smooth and musical.
Might I add...for electronica, one VERY cool effect which I use, tho not just in electronica-type settings) is the Roger Linn AdrenaLinn processor. MIDI/tempo syn'd filters and fx sequences...amp modeling and a drum machine all in one.
Max
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...it's not the arrow, it's the Indian.