Thanks for your hint: I didn't know that subtelty about Lucida OT (and I don't know how to set it up when using Lucida OT).

That being said, actually what I would like to use is the kind of script font which is the attached document (those script fonts were widely used in higher mathematics textbooks in France).

So when I use mkiv the result is the one I like and is attached to this message (test-scriptfonts-mkiv.pdf). However, thanks to your message I went to check, and noticed that lmtx does not give the same math script fonts, and I don't know what has changed between mkiv and lmtx regarding Asana Math, or the way in which fallback fonts are managed (please see the attached file test-scriptfonts-lmtx.pdf).

Thanks for your help: Otared

PS: this the the file test-scriptfonts.tex:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Some Font Definitions

\definefallbackfamily[myfont][math][Asana Math]

[range={uppercasescript,lowercasescript}]

% lucida font

\definefontfamily[myfont][serif][Lucida Bright OT]

\definefontfamily[myfont][math][LucidaBrightMathOT]

\definefontfamily[myfont][sans][LucidaSansOT]

\definefontfamily[myfont][mono][LucidaSansTypewriterOT]

%\setupbodyfont[myfont,10pt]

%% End of Font Definitions

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\starttext

\startbuffer[test]

Testing script fonts in maths

\startformula

x^2 + y^2 = z^2, \quad \sin(a)^2 + \cos(b)^2 = 1.

\stopformula

\startformula

\cal{A},

\quad \cal{B},

\quad \cal{C},

\quad \cal{D},

\quad \cal{E},

\quad \cal{F},

\quad \cal{G},

\quad \cal{H},

\quad \cal{K},

\quad \cal{L},

\quad \cal{M},

\quad \cal{P},

\quad \cal{S},

\quad \cal{T}

\stopformula

\hairline

\stopbuffer

\switchtobodyfont[lucidaot]

{\bf Lucida OT: }

\getbuffer[test]

\switchtobodyfont[myfont]

{\bf Lucida OT with Asana Math: }

\getbuffer[test]

\stoptext