Sennheiser HD428/448 (latter for better looks). Fits most of your criteria, plus they're not really expensive.

I have a digital piano (although I am nowhere near professional) and use my Senn HD555's with it.  They sound fantastic and are very comfortable, even playing for long periods.  Mine are about 5 years old and have developed a small crack on the left side, but it has not affected anything and I expect many more years of use.

I have also tried using Grado's, AT-FC700's, and Westone IEM's, but none of them sound as good or are as comfortable as the Sennheisers. 

This probably doesn't fit her requirements, but just my 2 cents.

Hmmm...I am a Senn 600/650 and AKG 701 lover for piano, chamber music, acoustic jazz, folk etc. and I am a woman so looks as well as comfortable fit matter to me as well. If I were going to get a pair of phones that sounded good without an amp and could fit around my neck, I would go for the Senn 598 which I just bought on a whim. I LOVE their looks (light yellow with burl wood "highlights" ie plastic) and the fit is very comfy for the smaller female head. I found myself wearing them around my neck for a while last week while doing some chore and I could definitely still hear them clearly! So maybe these are an option for your GF? I got mine on sale at J&R for $170 shipped.

another vote for the esw-9s if the budget allows, or if not the es7 (the black metal looks very good, should match the piano she plays as a bonus)

ESW-9 - Perfect, forgot about them

I play a yamaha clavinova clp-340 and have used it with my hd650s, k702, and fostex t50rp.  I prefer the 702 by a small margin over the 650. Though cheap, there is far too much reverberation in the t50rp without serious modding, which it doesn't sound like your girlfriend is willing to undertake.  I would also suggest an open phone over a closed or iem for comfort, especially as a professional musician she will likely be wearing them for long periods of time and not exactly sitting still.  Both the 702 and 650 are great headphones, but i think the 702 is unmatched for solo piano both for listening and practicing.  just my 2 cents...

Quote:

Originally Posted by zmd 

Sennheiser HD428/448 (latter for better looks). Fits most of your criteria, plus they're not really expensive.

actually yea, these were my first "Hi-Fi" cans and they were wonderful for piano.

Quote:

Originally Posted by mikeaj 

With all due respect, I think many suggestions are forgetting that these are for practicing the piano, not listening to the piano.  She probably isn't going to do any serious listening or tinkering with interpretations, timbres, articulation, etc. on the digital piano anyway, so sound quality shouldn't be too important.  I couldn't imagine playing piano while wearing anything as bulky (or heavy, even though these aren't particularly heavy) as the HD 580/600, K501/601/701-2, etc.  Someone else's mileage may vary, but personally I would be displeased.

 

Any reason not to use IEMs, assuming you can find the right tips?  If she frequently wears headphones around the neck, maybe supraaural sets just aren't working for her.

I dunno, I play guitar with circumaurals, I just don't headbang with them. Although cables, reagrdless of the can size, will get in the way of doing the "Mozart trick."

Maybe because she doesn't want the headphones to mess up her hair? Women are picky like that. :)

I like to wear my Westone 3 IEMs when practicing piano. IEMs are nice because you barely notice they're on. Also, try the Comply foam tips. Very comfortable fit.

The HD25-1 II are great in terms of sound isolation, but I find the clamping force a bit too much in terms of comfort, especially if I have to wear them for very long sessions. As a pianist myself, I'd feel much more comfortable with my AKG K240S, they are quite light and cost about the same as the HD555. ;)

Looks, custom IEM in her fave colour. Also, these are less obtrusive; I think doing the Mozart trick - hitting a note in the middle with the nose while both hands are on opposite ends - would be easy.