Chameleon and Sublime Chord like class

[emoplato]

I'm positive this won't work. Chameleon casting is not genuine casting, but Arcane/Divine Focus. See, Chameleon doesn't have its own casting. It has the Focus class features instead. To my knowledge, no class explicitly advances the Arcane/Divine Focus class feature. So the emulated arcane or divine (pseudo-)casting cannot be advanced in any way - except by "+1 existing class feature" advancement. That kind of advancement is found with Uncanny Trickster, Legacy Champion and maybe elsewhere, but it is very rare. Even with this kind of advancement, you won't be getting higher than 6th level spells, since that is where Arcane/Divine Focus cap out!

However, it is not impossible to reach higher level spells via some (to me) somewhat questionable tricks. Those tricks can be found in the Chameleon Handbook that @Sekhmet linked to.

Aptitude focus is the exchange of options you have to choose from which also have Arcane/Divine focuses. What makes this different though is that the spells gained is not dependent on the focus advancement. Selecting the focus just gives you access to spells which go up every level but focuses have other bonuses just for each one and go up at specified levels. The spells advance separately and conjointly so existing spellcasting progression would do just fine so long as they select the focus in which gives them access to the spells. You just can't use the Chameleon to qualify for other prestige classes. Neither can you advance other Chameleon abilities once you go into said PrC. It is why I pointed to a Dragonwrought Kobold Factotum Cleric because otherwise it can't. The ten level class gives you 6th level spells but it advances quite consistently and still has room to advance if you look on the table. The focuses also don't specify any cap, so as long as you have the respective mental scores you can cast higher level spells.