Re: MusicXML and MIDI

Hi Johannes,

Thanks for the detailed answer, which makes sense. We obviously believe
that profiles, whatever they are called, are essential to any framework or
language allowing a full spectrum of expressivity and consistency.

At the W3C meeting in Frankfurt we discussed that encoding profiles may
amount to more than simply support for a repertoire or subset of schema
elements -- they may also need to embody constraints that are not easily
expressible in a schema language, such as compliance between a measure's
time signature and the contents of its voices or layers (to take a very
CMN-specific example).

I look forward to attending MEC and hope that I'll get a chance to
participate in some of these discussions.

Best,

.            .       .    .  . ...Joe

Joe Berkovitz
President
Noteflight LLC

+1 978 314 6271

49R Day Street
Somerville MA 02144
USA

"Bring music to life"
www.noteflight.com

On Fri, Apr 8, 2016 at 1:31 AM, Johannes Kepper <kepper@edirom.de> wrote:

> Hi Joe,
>
>
> Zoltan,
>
> Is this notion of profiles literally a per-project matter?
>
>
> Not necessarily. There are generic profiles (we call them customizations)
> which restrict MEI to support only specific repertoires like CMN (which,
> for instance, requires the use of measures, which wouldn't be allowed for
> mensural notation). In essence, they identify a subset to be used.
> Individual projects, however, may use the very same mechanism to describe
> their specific use of MEI, that is, the subset of the generic subset
> they're actually using. This way, they're documenting their use of the
> format (which is more of a framework and really expects such customized
> use), and help to manage expectations for other consumers of their data.
> Likewise, applications may use this mechanism to define the subset of MEI
> they're able to understand, and by doing so are able to provide a schema
> that can be used as 'input filter', so users of the application can see
> beforehand which parts of their data will cause problems with this
> particular app.
>
> That said, our generic profiles are still not very 'narrow' yet, and there
> have been some discussions amongst the MEI developers to specify some
> 'tighter' profiles, which may support interchange both within MEI and with
> other formats. While this is still pretty much in the open, I expect this
> topic of more restricted profiles to be discussed during the Music Encoding
> Conference in Montréal in May, for instance.
>
> Hope this helps,
> Johannes
>
> .            .       .    .  . ...Joe
>
> Joe Berkovitz
> President
> Noteflight LLC
>
> +1 978 314 6271
>
> 49R Day Street
> Somerville MA 02144
> USA
>
> "Bring music to life"
> www.noteflight.com
>
> 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
>>>
>>>
>>>
>>
>> www.tido-music.com
>>
>> Tido Enterprise GmbH (Amtsgericht Leipzig, HRB 29529), Talstrasse 10,
>> 04103 Leipzig, Germany. Disclaimer: The information in this e-mail
>> including any attachments is confidential and may be legally privileged. If
>> you have received this message in error, please contact the sender
>> immediately and delete this message and any copies from your computer and
>> network. The unauthorized use, distribution, copying or alteration of this
>> e-mail and any attachments is strictly forbidden.
>>
>
>