nv = voice_tb.length,
	vtb = [],
	vn = [],			// voice indexed by range
	sy = cur_sy			// first staff system

	// check if different bars at the same time
	function b_chk() {
	    var	bt, s, s2, v,
		ir = 0

		while (1) {
			v = vn[ir++]
			if (v == undefined)
				break
			s = vtb[v]
			if (!s || !s.bar_type || s.invis
			 || s.time != time)
				continue
			if (!bt) {
				bt = s.bar_type

				continue
			}

			if (s.bar_type != bt)
				break
		}

		// if the previous symbol is a grace note at the same offset as the bar
		// remove the grace notes from the previous time sequence
		if (!fl) {
			while (prev.type == C.GRACE
			    && vtb[prev.v] && !vtb[prev.v].bar_type) {
				vtb[prev.v] = prev
				prev = prev.ts_prev

				fl = 1 //true
			}
		}

		if (v == undefined)
			return			// no problem

		if (bt == "::" || bt == ":|") {
			ir = 0