Changes from MusiXTeX 121 to 122:

 +  bi and sc font definitions added; sl and tt definitions for musixsty moved
 +  explicit font choices for \txtfont replaced by generic commands
    \smalltype\it etc.
 +  \pdlud \halfwidthbigwedge and \raise height font-dependent
 +  \zbreath and \cbreath use BIGtype rather than BIGfont