The best way to get Mp3’s into max is to import them into buffers- max doesnt like it, but its the only way it’ll take em. So the approach I’d use would be:
2 buffers~ – each with a unique name – you just send them an import command and they will take MP3’s
secondly, you need to decide how to play them, my money would be on groove~ as it allows you to edit playback speeds etc easily – this would give you good simple pitch control.
To pitch shift without changing pitch is less fun- you’ll need to use Gizmo~ through Pfft – but it does sound pretty good.
Finally to get bass and treble – can be as fiddley or as simple as you want it, just look at the list of filters and pick one.
Something like cascade~ with 2 n-filters will give you simple treble and bass, but you could go for a full parametric array if you wanted.
Hope this at least gives you an idea, If you need any help or examples just ask again, i’m not any where near my Max machine at the mo or would have come up with something simple now.