Define a sound transition. The duration is specified in multiples of 16ms, and the frequency and volume increments are applied every 16ms.
chan = Sound channel (0 - 3).
freq = Frequency (0 - 8191).
vol = Volume (0 - 1023).
finc = Frequency increment.
vinc = Volume increment.
durn = Duration of transition.
mode = 0 - Continue from previous frequency and volume (ignore new values).
mode = 1 - Start at specified new frequency and volume.
Include file: mtxsnd.h