Re: MusicXML and MIDI

Great summary by Andrew.

Joe also asks "*which timestamps can be relied on to be present in various
situations*"?

By default most attributes are optional in MEI. Hence, the recommended
practice that every project should use a customization, in other words a
restricted schema that specifies which attributes/elements are required. We
sometimes call such a customization an *application profile*, because it
describes the input interface of the application.

Zoltan


On Wed, Apr 6, 2016 at 5:54 PM, Andrew Hankinson <andrew.hankinson@gmail.com
> wrote:

> ...snip...
>
> > I note that MEI also addresses this question by supply a variety of
> different timestamps for musical events, including both metrical (notated)
> time and other assorted time bases; some tick-based (as with MIDI) and some
> millisecond-based. However it is not clear to me how these time bases are
> reconciled or what conventions exist for knowing which timestamps can be
> relied on to be present in various situations. Perhaps someone from the MEI
> community can speak to this.
>
> MEI treats durations and timestamps differently, and makes the distinction
> between logical and gestural durations.
>
> <note dur="4" dur.ges="256p" />
>
> Would indicate a quarter note with 256 MIDI pulses-per-quarter. A 'swung'
> quarter then might be:
>
> <note dur="4" dur.ges="264p" />
>
> Gestural durations can also be expressed in the case of beats or seconds,
> so dur.ges="3s" or dur.ges="1.5b" would also be valid.
>
> MEI relies on validation to ensure the proper values of attributes, and
> these values are determined by regex or built-in XML data types. So, for
> example, the "dur.ges" attribute is defined as an attribute which takes a
> data type of "data.DURATION.gestural":
>
>
> https://github.com/music-encoding/music-encoding/blob/develop/source/specs/mei-source.xml#L4587
>
> and this duration is composed of sub-types, validated by regex:
>
>
> https://github.com/music-encoding/music-encoding/blob/develop/source/specs/mei-source.xml#L875
> (and following).
>
> If a user or software puts "dur.ges=4", this will fail validation because
> the regex specifies gestural durations must have a number with an
> associated unit of either PPQ (p), beats (b), seconds (s), or humdrum beat
> proportions (r). This is all built into the schema, so one need only run a
> given encoding against the RelaxNG schema using any XML validator (xmllint)
> to determine whether or not a given duration is valid.
>
> For timestamps, we express duration as the passage of musical time
> expressed as beats and measures, so an object with "@tstamp=1m+2" would
> mean that that particular object began at an offset of 1 measure and two
> beats. Often you will get "@tstamp" and "@tstamp2" which allows an object
> to take a duration (e.g., a hairpin).
>
> -Andrew
>
>
>

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