The songs package does not natively support that functionality because, in general, the right-hand-side of any index entry might refer to multiple songs. This is less common in title indexes than in other indexes, but still happens occasionally. For example, in a book with three songs all entitled "You", the index entry looks like:
You.....3, 37, 218
The package only links the items appearing on the right-hand-side, since only those are guaranteed to have unique referents.
Changing this behavior entails redefining the internal package code's \SB@ellipspread
macro, which typesets ellipsis lines. (Redefining \songtarget
won't help you; that just creates the invisible destination marker to which hyperlinks point, not the links that point to them.) The following code (tested on songs version 2.18) successfully links the left-hand-sides of index entries that have exactly one referent on their right-hand-sides, but leaves left-hand-sides of other entries unlinked. I can't guarantee that it will work in all possible situations, since right-hand-sides of indexes could conceivably contain anything. But it works for the sample book I tested.
\newcommand\savetarget[2]{%
\gdef\mytarget{#1}%
\def\songlink##1##2{\global\let\mytarget=\relax}%
}
\newbox\dummybox
{\makeatletter
\global\let\oldellipsis=\SB@ellipspread
\gdef\SB@ellipspread#1#2{%
\global\let\mytarget=\relax
{\let\songlink=\savetarget
\setbox\dummybox\hbox{#2}}%
\oldellipsis{\ifx\mytarget\relax#1\else\songlink{\mytarget}{#1}\fi}{#2}%
}
}
\documentclass{...}
and ending with\end{document}
.