Disclaimer: I wrote the package described below.
Caveat emptor ...
cfr-lm provides access to all Latin Modern fonts supplied in type1 formats by TeX Live. This includes access to the 4 sets of figures, as well as various other features, including weights and widths not supported by LaTeX's New Font Selection Scheme.
For example
\documentclass[letterpaper]{article}
\usepackage[sf={lining,proportional},tt={monowidth,lining,tabular},rm={lining,proportional}]{cfr-lm}
\begin{document}
Is there an easier, simpler and more elegant way to switch font from \texttt{\textlg\textcd{{light condensed}}} to \texttt{\textlg{light}} to \texttt{medium} and to \texttt{\textbf{bold}} and, at the same time, preserve the default text font.
Or \texttt{\lgweight\cdwidth light condensed} to \texttt{\lgweight light} to \textt{medium} to \texttt{\bfseries bold}.
\end{document}

A variable width typewriter font is also available and may be more appropriate for this use than a mono-width one. (It is hard to know from the example.)
For code, mono-spacing is useful, but for typewriter text, it is less so.
\documentclass[letterpaper]{article}
\usepackage[sf={lining,proportional},tt={variable,lining,tabular},rm={lining,proportional}]{cfr-lm}
\begin{document}
Is there an easier, simpler and more elegant way to switch font from \texttt{\textlg{light}} to \texttt{medium} and to \texttt{\textbf{bold}} and, at the same time, preserve the default text font.
Or \texttt{\lgweight light} to \textt{medium} to \texttt{\bfseries bold}.
\end{document}

If you need to typeset code, you will need mono-width. However, cfr-lm provides commands which allow you to switch to a non-default font temporarily (i.e. using \textXX{} or {\fontswith } or until further notice (i.e. \fontswitch). This provides access to mono-width typewriter with tabular, lining figures in a document where \ttfamily is set to variable typewriting with proportional, hanging figures, for example.
You can also access some additional fonts e.g. the specialist 'quotation' font, the Latin Modern versions of the Dunhill fonts, slashed zeros, italic small-caps, upright italics and more. See the documentation for details.
Here's a more complete sampler.

\documentclass[a3paper]{article}
\usepackage{geometry,microtype}
\geometry{hscale=.9,vscale=.9}
\usepackage[sf={lining,proportional},tt={variable,lining,tabular},rm={lining,proportional}]{cfr-lm}
\newcommand*\nos{0123456789\zeroslash}
\newcommand*\tester[1][]{\noindent{{\normalfont\texttm{cfr-lm}} #1provides easier, simpler and more elegant ways to switch between Latin Modern fonts. \textpo{\nos{}} \textpl{\nos} \textto{\nos} \texttl{\nos}\par}}
\begin{document}
\section*{Roman}
\tester
\tester[\slshape]
\tester[\itshape]
\tester[\uishape]
\tester[\scshape]
\tester[\sishape]
\tester[\bfseries]
\tester[\bfseries\slshape]
\tester[\bfseries\itshape]
\tester[\sbweight]
\tester[\sbweight\slshape]
\section*{Sans}
\sffamily
\tester
\tester[\slshape]
\tester[\bfseries]
\tester[\bfseries\slshape]
\tester[\fontseries{sbc}\selectfont]
\tester[\fontseries{sbc}\selectfont\slshape]
\normalfont
\section*{Monowidth Typewriter}
\tmstyle
\tester
\tester[\slshape]
\tester[\itshape]
\tester[\scshape]
\tester[\sishape]
\tester[\bfseries]
\tester[\bfseries\slshape]
\tester[\lgweight]
\tester[\lgweight\slshape]
\tester[\lgweight\cdwidth]
\tester[\lgweight\cdwidth\slshape]
\normalfont
\section*{Variable Typewriter}
\ttfamily
\tester
\tester[\slshape]
\tester[\bfseries]
\tester[\bfseries\slshape]
\tester[\lgweight]
\tester[\lgweight\slshape]
\normalfont
\section*{Dunhill}% the documentation erroneously claims a bold version is available - it doesn't exist
\tistyle
\tester
\tester[\slshape]
\normalfont
\section*{Quotation Sans}
\qtstyle
\tester
\tester[\slshape]
\tester[\bfseries]
\tester[\bfseries\slshape]
\normalfont
\end{document}
{...}. I suggest to use macros with an argument here, however – Sep 04 '16 at 23:42\textXXto create/generate\lightfont– Igor Sep 05 '16 at 06:58