The alto flute is the only instrument I know of that is pitched in the key of G. Why is this so?

For recorders, the alto and bass (and sopranino, too) are pitched in F. Also the lower-pitched relative of the oboe, the English horn, is pitched in F.

I have done some thinking on this matter, and here are some of my guesses as to why it is in G:

1. It is shorter in length (and hence lighter in weight) than if it were in F.
2. Flute music at the time was written in more sharp keys (G and D), so it was easier to play than if it were in F.
3. It was designed for compatibility with Irish flutes, of which most are in D.

Of these, I think #1 explains it best. What do you think?

IMHO the G flute is already so big and demanding that a F instrument should be carried by 2 flutist!

There's a Contrabass flute in G, they're really rare though.

I've always woundered why the alto flute was only a fourth lower then the C flute. It seems like there would be a large gap in pitch between the alto flute and the bass flute.

The only answer i can think of is; the bass flute is pitched higher than any other bass instrument, so the alto flute would have to be pitched higher. Though it still feels like there's a gap.

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Unless the alto was made before the bass. I'm not sure which was made first.

The alto flute was indeed produced before the bass. In fact, up until the bass was created somewhere around 1930, the alto flute was called a "bass flute". Holst's original score for The Planets called for a "bass flute," but the part is actually played on an alto, simply because the bass didn't come out for more than a decade after the suite's premier. Why anything is pitched in the key it is is a difficult question to answer. Why are trumpet, clarinet, tuba, string bass, etc. in Bb? Why aren't they in the key of F or the key of Db, or the key of Ab, or or or? The only possible reason I can give is that when the alto was first developed, the lowest flute they had the technology and skill (and probably desire) to produce was in G. Larger flute pose some technical challenges, from acquiring or producing the necessary tube size and thickness, to make the necessary modifications to the mechanism so that a human hand can activate the keys it needs to activate. Then there is the concern of length. Curved heads a re a relatively recent innovation, so most older altos had straight heads. For smaller players, altos with straight heads are already a stretch, so dropping it into the key of F would call for extra length, making it even more unwieldy to play for all but the largest of players.