def midiEventsToKeySignature(eventList):
'''Convert a single MIDI event into a music21 TimeSignature object.
>>> from music21 import *
>>> mt = midi.MidiTrack(1)
>>> me1 = midi.MidiEvent(mt)
>>> me1.type = "KEY_SIGNATURE"
>>> me1.data = midi.putNumbersAsList([2, 0]) # d major
>>> ks = midiEventsToKeySignature(me1)
>>> ks
<music21.key.KeySignature of 2 sharps>
>>> me2 = midi.MidiEvent(mt)
>>> me2.type = "KEY_SIGNATURE"
>>> me2.data = midi.putNumbersAsList([-2, 0]) # b- major
>>> me2.data
'\\xfe\\x00'
>>> midi.getNumbersAsList(me2.data)
[254, 0]
>>> ks = midiEventsToKeySignature(me2)
>>> ks
<music21.key.KeySignature of 2 flats>
'''
# This meta event is used to specify the key (number of sharps or flats) and scale (major or minor) of a sequence. A positive value for the key specifies the number of sharps and a negative value specifies the number of flats. A value of 0 for the scale specifies a major key and a value of 1 specifies a minor key.
from music21 import key
if not common.isListLike(eventList):
event = eventList
else: # get the second event; first is delta time
event = eventList[1]
post = midiModule.getNumbersAsList(event.data)
if post[0] > 12:
# flip around 256
sharpCount = post[0] - 256 # need negative values
else:
sharpCount = post[0]
environLocal.printDebug(['midiEventsToKeySignature', post, sharpCount])
# first value is number of sharp, or neg for number of flat
ks = key.KeySignature(sharpCount)
if post[1] == 0:
ks.mode = 'major'
if post[1] == 1:
ks.mode = 'minor'
return ks
def midiEventsToTimeSignature(eventList):
'''Convert a single MIDI event into a music21 TimeSignature object.
>>> from music21 import *
>>> mt = midi.MidiTrack(1)
>>> me1 = midi.MidiEvent(mt)
>>> me1.type = "TIME_SIGNATURE"
>>> me1.data = midi.putNumbersAsList([3, 1, 24, 8]) # 3/2 time
>>> ts = midiEventsToTimeSignature(me1)
>>> ts
<music21.meter.TimeSignature 3/2>
>>> me2 = midi.MidiEvent(mt)
>>> me2.type = "TIME_SIGNATURE"
>>> me2.data = midi.putNumbersAsList([3, 4]) # 3/16 time
>>> ts = midiEventsToTimeSignature(me2)
>>> ts
<music21.meter.TimeSignature 3/16>
'''
# http://www.sonicspot.com/guide/midifiles.html
# The time signature defined with 4 bytes, a numerator, a denominator, a metronome pulse and number of 32nd notes per MIDI quarter-note. The numerator is specified as a literal value, but the denominator is specified as (get ready) the value to which the power of 2 must be raised to equal the number of subdivisions per whole note. For example, a value of 0 means a whole note because 2 to the power of 0 is 1 (whole note), a value of 1 means a half-note because 2 to the power of 1 is 2 (half-note), and so on.
#The metronome pulse specifies how often the metronome should click in terms of the number of clock signals per click, which come at a rate of 24 per quarter-note. For example, a value of 24 would mean to click once every quarter-note (beat) and a value of 48 would mean to click once every half-note (2 beats). And finally, the fourth byte specifies the number of 32nd notes per 24 MIDI clock signals. This value is usually 8 because there are usually 8 32nd notes in a quarter-note. At least one Time Signature Event should appear in the first track chunk (or all track chunks in a Type 2 file) before any non-zero delta time events. If one is not specified 4/4, 24, 8 should be assumed.
from music21 import meter
if not common.isListLike(eventList):
event = eventList
else: # get the second event; first is delta time
event = eventList[1]
# time signature is 4 byte encoding
post = midiModule.getNumbersAsList(event.data)
n = post[0]
d = pow(2, post[1])
ts = meter.TimeSignature('%s/%s' % (n, d))
return ts
