So my buddy's gonna go into the studio and he's got this track where he wants to really play with feedback. He asked me if I thought string's would matter at all since he's trying to get the feedback to "play" the strings.
My first instinct is to use super light strings because they have less mass and would be easier to excite from speaker vibrations.
BUT I don't have lots of experience with this so I thought Id ask you guys.
I don't think it matters. Feedback is a combination of volume and gain/saturation.
Your best bet is to crank up your amp, then walk around the room holding the note you want to feed back and wait for it to "bloom" and start feeding back.
Barring that, you can artificially increase feedback by touching the neck of the guitar to the speaker cab, though you have to be careful about this not to knock it against the cab and capture that sound.
Also, if he knows exactly what he wants in terms of notes, there's always the Ebow...?