I am trying to learn Crested Hens and I am confused on how to play D#.
You have to half-cover the lowermost tonehole.
XXX XX/
All holes closed, last hole half-covered.
aka Eb?
Yes, that is the enharmonic equivalent. AFAIK, when you have a sharp key (key sig of D=2 sharps) the accidental will be a sharp as well. So D# not Eb.
Cheers 
David
The reason why it’s called D# and not Eb is because of some old rule about keys using a given note once and only once. Having an Eb then E would be two uses of the E note. I think that rule also explains why you see double sharps/flats. For instance a G## would be a B note, but it’s not written as a B because there’s already a B in the key.
Edit: No wait, a G## would be an A…right? I’ve never actually played a song with a double sharp, so I’m just going on what I’ve heard.
If you don’t want to half hole the D#, you could have a whistle maker drill a D# hole for you! But I don’t recommend it.
Try partially covering the D hole with a straight ring finger, touching the edge of the hole with the first joint instead of the pad. With practice, you can do it fairly accurately even on fast tunes. You just have to get the angle of your finger right and it gets easy with practice.
By the way, you can also get a nice A flat (works better on the upper octave) by covering xx0 xx0 It shows up in Sweeny’s Buttermilk, Jenny’s Chickens, and Kitty Come Down from Limerick, to name three.
Tony
Ok. On piano and viola (my childhood instruments,) it’s extremely rare to play in a key with more than 4 sharps, whereas playing Eb is quite common. Ever since, I picture the relative positions of notes on a mental keyboard.
Just for pedantry’s sake, the difference between D# and Eb is a couple of cents or so. Same with Bb and A#, or G# and Ab. Not that anyone other than someone with perfect pitch would notice.
Dear David & Emily,
You people are doing a great job of confusing the heck out of me. I’m not a musician. To deconfuse me, would someone please answer this one question: My limited understanding is that a D# and an Eb are the same note (i.e. produce the same tone when played), regardless of what name you want to assign to them. Is this correct? 
Signed,
Confused
Dear Confused: See Nano’s post above. I didn’t know that as all my theory stems from piano keyboard mentality.
As far as fixed-tuning instruments such as piano or accordion are concerned, Eb and D# are necessarily and functionally the same. What meager theory I have tells me that they are actually a teensy bit different, but it’s not important enough to lose sleep over. All that’s left to distinguish them is key signature. As far as I’m concerned, there’s no audibly appreciable difference.
Thank you, Emily. Nano must have posted while I was still typing. Thank you also, Nano. I think you pretty much agree with me that the D# and Eb are the same. Anyway, the way I play, if it sounds close then it’s in tune. And if it’s not in tune, I just need another beer.
Signed,
Deconfused
Yes, beer resolves all. 
Re: D# vs. Eb and their place in a key
While technically the “same note” (we’ll get more into that later 
)…the spelling has more to do with where it’s headed…a D# is headed upward to E…and Eb is headed downward to D. You’ll find both alterations in any given key, but they each show where they’re headed to.
As for them being the same note…on something like a piano, they are…generally with instruments like fiddle, a D# will be slightly higher than the pitch to aid in its motion upward, and Eb will be slightly lower to aid in its motion downward.
~Crysania
Will, you are now officially deconfused. They are the same. Ignore anything that suggests otherwise.
I’d have thought the question whether to call a note D# or Eb had to do with the key the piece was written in and the very sensible desire to reserve lines and spaces in standard notation for a note named in a way one has been taught to associate with that line or space. So, eg, in D major the C spot is going to be reserved for C# whilst in C major it is reserved for C nat.
Except you’re still taking a line or space that has a note on it…D# would take over the D line/space…an Eb would just take over a different one. So either way, you’re getting a chromatically alteration of a note that’s already in a key. So it really has more to do with its tendency to pull upward or downward.
And besides, why discuss music notation…I thought reading from the “dots” was all against the law at sessions…lol
~Crysania
If you’re playing in E major you would have both E and Eb? Which note get’s the E line? You can always avoid this problem no matter what key you are in by judicious choice of name for notes. Unless we followed the established conventions for calling notes flat or sharp depending on the key our whole system of indicating key by signature would break down.
What I find interesting is that we always seem to use the flat name for black key notes except F# when talking about them with no particular key in mind. So we talk of Eb, Db, Bb, Ab but F#. I think the same explanation applies here. We think about them as we are forced to when they are they are first note of the scale.