I use macro and titlesec package to create custom \section heading.
\documentclass[final]{book}
\usepackage{lipsum}
\usepackage{titlesec}
\titlespacing*{\section}{0pt}{1em}{0.3em}
\def \mysection#1{
\section*{\large{#1}}
}
\begin{document}
\mysection{Lorem ipsum dolor sit amet, consectetur adipisicing elit doloribus odio aliquid aut.}
\lipsum[2]
\mysection{Another section heading with very long text within it that wraps to second line}
\lipsum[3]
\end{document}
which produces

I want to be able to decrease or increase line spacing between lines of that \section heading.
I have tried to do so, by changing \mysection macro to:
\def \mysection#1{
\section*{\baselineskip=2pt \large{#1}}
}
but it doesn't have any effect. (Note that I set \baselineskip to 2pt only to spot it for sure when change happens, not because it is my target line spacing).
I have also tried to change it to:
\def \mysection#1{
\section*{\linespread{0.1} \large{#1}}
}
which seems to have slight effect on line spacing, but produces nasty indent out of nowhere:

I have also tried using setspace package with its command \singlespacing:
\documentclass[final]{book}
\usepackage{lipsum}
\usepackage{titlesec}
\usepackage{setspace}
\titlespacing*{\section}{0pt}{1em}{0.3em}
\def \mysection#1{
\section*{\singlespacing \large{#1}}
}
\begin{document}
\mysection{Lorem ipsum dolor sit amet, consectetur adipisicing elit doloribus odio aliquid aut.}
\lipsum[2]
\mysection{Another section heading with very long text within it that wraps to second line}
\lipsum[3]
\end{document}
which decreases line spacing, but adds unexpected white space above \section headings:

Is there any reliable way to modify line spacing of \section headings? I thought that titlesec should be able to do it, but I haven't found a clue how to do it in its documentation.


\baselineskip=2ptindicates the total distance between baselines, so with any type of readable size, it's quite impossible.\baselineskip=2cmshould have an effect, but if the expansion of\sectiondoesn't end with\par(i didn't check), then it wouldn't have any effect anyway. – barbara beeton Jun 03 '14 at 13:16