Is there such thing as...

[Heavy_Soul]

a phaser that only phases when you actually play notes?

for example, a small stone phases the signal the whole time, so a pedal that is just phasing when you play notes?

[StudioShutIn]

I think the Pigtronix EP-2 does that...it's an 'envelope phaser', i.e. trigger by pick-attack. You might also look at the Toadworks Phantasm...it does a similar thing..

[Heavy_Soul]

Sweet! I had a go on a Phantasm ages ago, killer little pedals, shame I wasn't looking for that particular sound back then as I had a chance to buy it too.

Thanks for the suggestions!