Set the font to monospace: and then the characters will align.

You could write a beat line and then use dots and crosses. You can get a dot with most keyboards by pressing and holding down the Alt Gr key and then typing a full-stop.

To get a line break in Markdown you type three spaces and then press Enter/Return. This makes the two lines closer together.
 
[mus]1 + 2 + 3 + 4 + 5 +[/mus]   
[mus]* · · * · * * · * ·[/mus]