OK, I got it going by using the following config

[hijack]
extmute_on=0x74
extmute_off=0x73
[ir_translate]
73.M=Auxiliary.S,null
73.T=Auxiliary.N
74.S=Auxiliary.S,Player.N,null
74.A=Tuner.N,null

This works most of the time but sometimes when switch back to the player, it switches back to the player but then goes to the tuner and when switching back to the tuner it sometimes starts flicking between AM & FM, this stops after about five oscillations.

What would be nice would be a savestate & restorestate option (and have it save/restore the volume level) so I could do it like this

extmuteon=savestate,Auxiliary,null
extmuteoff=restorestate,null

Thanks again,