for (i = 0; i < first.parts.length; i++) {
					if (first.parts[i] == v)
						first.p_s[i] = s
				}
			}
		}
	} // build_parts()

	// update the time linkage when the start time has changed
	function relink(s, dt) {
	    var	tim = s.time + dt,		// new time
		s2 = s.ts_next

		s.ts_prev.ts_next = s2		// remove from the time linkage
		s2.ts_prev = s.ts_prev

		while (!s2.seqst && s2.ts_next)
			s2 = s2.ts_next
		if (s2.time < s.time + dt)	// don't move after the next time seq.
			dt = s2.time - s.time
		s.time += dt			// update time and duration
		s.dur -= dt
		s.ts_prev = s2.ts_prev		// update the time linkage
		s.ts_prev.ts_next = s
		s.ts_next = s2
		s2.ts_prev = s
		s.seqst = 1 //true
		if (s2.time == s.time)
			s2.seqst = 0 //false
	} // relink()

	// generate the grace notes
	function gen_grace(s) {
	    var	g, i, n, t, d, s2,
		next = s.next

		// before beat

			d = next.dur / 12
			if (!(d & (d - 1)))
				d = next.dur / 2	// no dot
			else
				d = next.dur / 3
			if (s.p_v.key.k_bagpipe)
				d /= 2
			relink(next, d)

		}
//fixme: assume the grace notes in the sequence have the same duration
		n = 0
		for (g = s.extra; g; g = g.next)
			n++
		d /= n * play_fac
		t = p_time