Speaking of which, the example I posted had the original Pioneer codes wrong, so just for completeness, here is the correct version (for anyone with a Pioneer cu-vsx043 IR remote):

[ir_translate]
;Multiple simultaneous translations for TapeSelect button on Pioneer cu-vsx043 IR remote
a15e4c.LT=20df07 ; If (L)ongpress and (T)uner active, then toggle AM/FM
a15e4c.A=b9461e ; If (A)ux active, then select Main/mp3
a15e4c.M=b9461c ; If (M)ain/mp3 active, then select Tuner
a15e4c=b9461d ; default: select Aux