Re: MusicXML and MIDI

Zoltan,

Is this notion of profiles literally a per-project matter?

.            .       .    .  . ...Joe

Joe Berkovitz
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On Wed, Apr 6, 2016 at 1:34 PM, Zoltan Komives <
zoltan.komives@tido-music.com> wrote:

> 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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