Replace a few math symbols in the newtxmath font

Question

I use the \newtxmath as the math font in my document and \newtxtext for the text. This seems to work fine, but I need to replace some math symbols which seem to me not as nice as their default Latin Modern Math counterpart. The symbols I need to replace, e.g., are:

• \int and \sum: they look so high and big,
• \infty: looks too small, and
• \partial and \pi: looks strange too.

I have searched for similar or near question like this one (Replace several letters in math font), but I haven't been very successful in reusing the answer therein in my case.

My MWE is:

\documentclass{scrartcl}
\usepackage{amsmath,amssymb}
\usepackage{newtxtext,newtxmath}
\begin{document}

\noindent
ABCDEFGHIJKLMNOPQRSTUVWXYZ \\
abcdefghijklmnopqrstuvwxyz \\
$abcdefghijklmnopqrstuvwxyz$ \\
$ABCDEFGHIJKLMNOPQRSTUVWXYZ$ \\
$a\alpha\beta\gamma\delta\epsilon\varepsilon\zeta\eta\theta\vartheta\iota\kappa\varkappa\lambda\mu\nu\xi o\pi\varpi\rho\varrho\sigma\varsigma\tau\upsilon\phi\varphi\chi\psi\omega$ \\
$\Gamma\Delta\Theta\Lambda\Xi\Pi\Sigma\Upsilon\Phi\Psi\Omega$ \\
$\mathbb{ABCDEFGHIJKLMNOPQRSTUVWXYZ}$
\[
  \frac{1}{2\pi i}\int_\gamma f(x) = \sum_{k=1}^m n(\gamma;a_k) \cdot \text{Res}(f;a_k).
\]
\[
G(\omega)=\int_{-\infty}^{\infty}g(t)e^{-j\omega t} dt
\]
And this is nonmath text.

\end{document}

I appreciate your help.

Answer 1

The case \int is trivial, because there is an option cmintegrals for package newtxmath. In the other cases, the symbol fonts are overwritten by newtxmath. Therefore the example again defines them with a different name (CM appended):

 \documentclass{scrartcl}
\usepackage{amsmath,amssymb}

\usepackage{newtxtext}
\usepackage[cmintegrals]{newtxmath}

%% \sum
\DeclareSymbolFont{largesymbolsCM}{OMX}{cmex}{m}{n}
\let\txsum\sum
\let\sum\relax
\DeclareMathSymbol{\sum}{\mathop}{largesymbolsCM}{"50}

%% \infty
\DeclareSymbolFont{symbolsCM}{OMS}{cmsy}{m}{n}
\SetSymbolFont{symbolsCM}{bold}{OMS}{cmsy}{b}{n}
\let\txinfty\infty
\DeclareMathSymbol{\infty}{\mathord}{symbolsCM}{"31}

%% \partial, \pi
\DeclareSymbolFont{lettersCM}{OML}{cmm} {m}{it}
\SetSymbolFont{lettersCM}{bold}{OML}{cmm} {b}{it}
\let\txpartial\partial
\DeclareMathSymbol{\partial}{\mathord}{lettersCM}{"40}
\let\txpi\pi
\DeclareMathSymbol{\pi}{\mathord}{lettersCM}{"19}

\begin{document}

\begin{align*}
  \text{CM} &= \text{TX} \\
  \int \\
  \sum &= \txsum \\
  \infty &= \txinfty \\
  \partial &= \txpartial \\
  \pi &= \txpi
\end{align*}

\end{document}