A simple example of an svg font. A few things to note here:
<svg xmlns="http://www.w3.org/2000/svg">
<font id = "myFont"
horiz-adv-x = "1000"
vert-origin-x = "0"
vert-origin-y = "0" >
<font-face font-family = "myFont"
font-weight = "normal"
units-per-em = "1000">
<font-face-src>
<font-face-name name="myFont"/>
</font-face-src>
</font-face>`
<glyph unicode="a" d="M0 0 H1000 L500 1000z M200 200 L500 800 L800 200z" />
<glyph unicode="b" d="M0 0 H1000 L500 1000z M200 200 L500 800 L800 200z" />
</font>
</svg>
If you have wider or narrower glyphs, just change the horiz-adv-x on the glyph element itself.
<glyph unicode="a" horiz-adv-x="512" d="M0 0 H1000 L500 1000z M200 200 L500 800 L800 200z" />
the unicode property is used for later glyph selection. You can use simple letters or unicode codepoints as well as ligatures (combination of letters or unicode codepoints)
unicode="abc"
unicode="ab"
unicode="abab"
unicode="a"
unicode="b"
glyphs are always selected by first match, so do have all ligatures before any single character.
unicode codepoints can be written in decimal {
or in hexadecimal 
notation.