why are symbols like the long vowels (vowels with a macron) and schwa not in the standard character sets for fonts?

Probably because most users don't want or need them...

So, I suppose a broader question this brings up is: why are symbols like the long vowels (vowels with a macron) and schwa not in the standard character sets for fonts?

Because they’re very rarely used. Thus it makes sense for the specialists who need these characters to pay the cost of developing them.

Most of them are simple modifications of other letters, no?

There are no simple modifications of letters. A letter can’t just be flipped or warped a little and still look good; thought has to go into it. And then it has to be proofed and edited. And kerning must be taken into account; characters with funky shapes and stuff above or below can’t just be thrown into regular kerning classes. In a family, this has to be done for every master and checked again in every interpolation. So, depending on the design of the font, you’re probably looking at at least five minutes of work, and possibly much more, per character, for every single font within a family. And now that everything is global this stuff can’t just be limited to what Western Europe and North America uses; it has to work and be checked with dozens of languages. And none of that accounts for all of the research that goes into figuring out how all these characters are used so that they can be produced and tested. That is why characters like schwa, symbols for typesetting complex equations, and letters/accents for dead languages aren’t going to start turning up in most fonts any time soon.

James, let me disagree partially with you. Some characters are really simple variations from another ones, even about kerning and spacing. But others just seems to be simple.

And about characters support, I also think we're still highly determined by Western European culture. Some largely used non-European languages, with write tradition and using Latin alphabet, are fairly marginal to our type standards, while some almost extinct languages from Europe deserves a lot of attention both in Unicode and in type tradition.

I believe this would slowly improve with time, with more and more fonts with a wide language support.

Chris, the technical limitation you’re asking about is called ‘time’.

The new Premium Open Type font standard from Font Bureau includes the schwa. I know Benton Sans and the two new fonts that have just been released have it, as well as the macron over the vowels.

I have put schwas in several fonts, and IMO it isn't a simple modification.
Perhaps if your font is the kind where d rotates to p, then the scwha is simple, but otherwise...

Just out of curiosity - what kind of schwa do you have in mind: IPA, SAMPA, Hebrew ... ?

As these are latin fonts, it is the rotated e, not the two dots vertically aligned of Hebrew. Looking up SAMPA, they seem to use the @ sign, so there would be no additional glyph needed for that.

Hello all, thanks for the comments. I hope that anyone here who's met me knows that I understand the work that goes into a single weight, let alone a full family, so I realize that every little bit inflates this large time commitment further. Your answers make sense, and I anticipated it would be basically a matter of spending time on the most needed glyphs. I was curious if there are technical limitations, but clearly there are not (or no longer are).

I also realized, after I posted, that this is another case of "if you start with one, you have to finish with dozens", so it makes sense that pronunciation characters would be pretty uncommon.

Which leads me to a question: any pointers for creating one's own schwa? I'm setting a dictionary-style definition that'll be set in roughly 50pt type, so I'd like it to look good when shown at full size. So far, the only typeface in my library that I've come across which actually contains a unique schwa (rather than a simple rotation) is Garamond Premier Pro (thank you, Adobe). It looks like the primary structural differences between the e and the schwa are:

1) A larger counter, which raises the horizontal stroke in the schwa
2) The aperture of the schwa is a hair more open, as the lower stroke doesn't curl back in as much before terminating
3) The thin of the lefthand stroke of the schwa is thicker, but this is also likely a function of this particular typeface's stroke axis

Any other things to be mindful of?

Cheers.

I think you have to figure this out for yourself, Chris, based on your own taste and understanding of typographic logic.

In Oneleigh, it seemed to me that a simple rotation of "e" was out of character with an irregular old style face.
So I made the top left terminal more like that of "a" (for micro-detail following letters such as "r" and "t"), and enlarged the bowl, to make it less like the "a" when viewing text en masse.

I usually adjust the relative counter space in the schwa, as Nick has done, and optically adjust the weight transition and curvature going from the top into the right side, but I generally avoid a terminal on the upper left.

For the font project I'm doing, I choose to use an inverted |e| to lowercase without further edition. Its bar is almost in the middle and it seems to fit overall design.

But for the uppercase I buit a completely new glyph to match other glyphs characteristics:

"I generally avoid a terminal on the upper left"

Imteresting – I've been wondering about that. Would you care to share why?
And, do you mean in the cap, too?

Thanks, all. These are just what I was looking for: examples of the thinking process and issues, which I prefer over a "do this" solution.