A key does exactly the same as opening a fingerhole does. Think of the keys as a set of extra holes and extra fingers. The holes that the keys open are placed between the normal holes, thus achieving the semi-tones.
A keyed simple system flute works exactly like a normal one until you open a key. You might have to alter your grip slightly, but I haven’t found it to be a problem myself.
The most common keys depend entierly on what modes you usually play in. I would say Cnat is the most common, followed by Fnat.
Have a look at Terry McGee’s site. He has extensive information about everything flute related.
On a 6 key flute, the keys will usually get you Eb, two versions of Fnat, G#, Bb and Cnat.
To be fully chromatic on a keyless flute, you really only need 4 keys (Eb, Bb, G# and one of the Fnats).
Which keys are most commonly used really depends upon the player - unlike Henke, I rarely use the Cnat on my flute - I still prefer to finger OXX OOO for Cnat.
I thought baroque flutes were fully chromatic with one key. Am I miss understanding something?
Yeah, you’re missing three keys…
But seriously, they are chromatic, but I had already jumped the gun and assumed we were talking larger bore classical/ITM types of flutes which need 4 keys to be chromatic.
The baroque flute is chromatic with one key (Eb) and requires some extensive flute gymnastics (lots of cross fingerings and rolling in/out and breath control) to be chromatic. Don’t get me wrong, when well played they are wonderfully chromatic - when played by me, well, there’s a reason I sold my Grenser. I like the larger bore flutes that need those extra keys to be chromatic.
Not sure what you mean about the “D” key, but for me as an Irish flute player here is how I’d list the keys in order of most-used to least-used:
First, by far, the long F key. Then the short F key. Third, the G# key. Next, probably a tie between the C natural and Bb keys. I personally have never used my D# key.
Other flute players may give you a different ordering, although probably all would agree that if you can only have one F key it needs to be the long one. Also, if you’re playing an old orchestral flute rather than a new wooden flute made specifically for Irish music, you may need the D# key so you can vent it to get other notes to sound in tune.
Hammy Hamilton, the well-known flute maker, wrote a book a decade or so ago called The Irish Fluteplayer’s Handbook that covers most of these topics. (Prices change, so you’d probably be best off getting a handle on those by monitoring sites like Chiff and Fipple and eBay rather than from a book.) Unfortunately, Hammy’s book is now out of print, but his website ( www.hamiltonflutes.com ) reports that a reprint is now in the works. Keep posted! Meanwhile, Brad Hurley’s flute site is a great resource and pointer to information: www.firescribble.net/flute .