add method
Implementation
Timing add(Timing timing) {
if (type == timing.type) {
return Timing(type, nth + timing.nth);
} else {
final sixteenthNth = toSixteenthNth() + timing.toSixteenthNth();
assert(sixteenthNth < 17);
return Timing.ofSixteenthNote(sixteenthNth);
}
}