Yamaha TG500 Owner's Manual page 256

UTILITY MODE / WAVE EDIT MODE / 2: Sample
Type (Loop type)
244 SAMPLE
Range: Nrm, Alt
This parameter is only available when either the "FLp" or "BLp" loop type
is selected (see "Loop", above). When set to "Nrm" (normal), the sample is
repeatedly looped in either the forward or reverse direction, as specified by the
Loop parameter. If "Alt" (alternate) is selected, the sample is alternately played
forward and backward.