Band-in-a-Box (and similar).

Band-in-a-Box (and similar intelligent arranger software) works very
well with microtonal ideas when the sound device is tuned externally,
connected via midi and restricted to 12-note sets of ANY equal
temperament. This might severely limit some composers but when it comes
to composing short, lyrical pieces having only 12-notes of ANY equal
temperament at one's disposal is often more than enough.