The SCD world is lucky to have two musicians called Ian Muir both of whom also compose tunes:  
<<ddp:Muir, Ian R#1590>> (Craigellachie)  
<<ddp:Muir, Ian T#1575>> (Prestwick)  

This entry should ideally not be used for either of them. If database editors come across any tunes with composer only given as "Ian Muir" they should try and find out which one it actually was and only enter it here if they are not able to do so.