Mike Fugazzi wrote:
From direct experience - Boss OC 2 or the octaver on my M13 work great for this.
Disadvantage of the OC2 is that the sound of the dry signal
when the fx is on is very poor.
(I never used the one I had much because in bypass
my sound was significantly degraded)
afaik the OC2 is replaced by the OC3, which on a brief trial
didn't seem to suffer the faults of the OC2 mentioned above.
The EHX stuff is delayed and will kill timing your loops.
I use the Octave Multiplexer all the time, no delay.
...but that's on guitar.