Hmm, I always considered these markings as the little extra bonus that the original Jazz Font had to offer above the initial Sibelius Inkpen Font. And I note that the example picture of the petaluma font on the smufl page has the word “Intro” within these brackets, so there seems to be an awareness of the importance.
Actually I can use the Jazz Font. I even can use only the three bracket elements from the Jazz Font together with petaluma script, which is tedious though, as you have to manually switch between Petaluma and Jazz Font after every single character, and it is sub-optimal because the “connection line” which works using zero-width is not actually zero-width, so a little extra space is added between each character.
And unfortunately this approach would be impossible for automatic generated texts like “To Bb Clarinet”, as it is not possible to mix fonts there, so the only workaround here would be to hide the automatic text and replace it with a staff text.
how much effort would it take on your side to provide 2 stripped down versions of the Petaluma script, one where the underlined single letters (without the ligatures) are mapped to the unicode points of the regular alphabet, and one for the ones with the line above, so that for simple texts we could use them just like a regular font? The opening and closing brackets should be mapped within the unicode standard range, so they could even be included as pre- and suffix of my instrument change example.
I think this would work quite well as an interim solution.