Post

Something like this:

[clock] -- [clock divider/multiplier] -- [seq2]
|
[seq1]

would do that.
Where seq1/2 are two sequencers playing the same sequence at two different but related speeds,
one being a integer division or multiple of the clock. That way you would be able to not only vary the speed ratio between your two copies of the sequence in a wide range but to do so in real time using a CV source like another sequencer (or LFO, envelope, manual offset, ...) while keeping the parts in sync.