according to [the simai spec of holds](https://w.atwiki.jp/simai/pages/1002.html#id_9a6db170), you can specify the bpm in which the hold duration is specified.  but currently, simaisharp does not accept this syntax. 
according to the simai spec of holds, you can specify the bpm in which the hold duration is specified.

but currently, simaisharp does not accept this syntax.
