Detuning is playing a number of oscilators slightly offset in pitch and combining them back together to create artificial harmonics. The tune knob on the TB is used to tune the synth into whatever else you're using, or do a simple transposition. Transposition doesn't really alter the way something sounds relative to it's context, it lowers or raises the key. So Mary Had a Little Lamb will have the same sound in the key of A as in the key of C for example.. magor. The feel is dependant on the scale, not the key.