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This week’s quiz is to create a polyrhythm training program. The user
will be prompted to tap out a rhythm with two keys: left and right.
Each time the user presses a key the program will display how close to
the correct timing the key press occurred. The program will be
configurable to train the user in any polyrhythm 2:3, 5:4, 11:17, and
so on. The program will also have a configurable tempo. After a number
of complete rhythms the program will display the ratio of how many
notes were successfully struck, success determined by being within a
threshold around the perfect timing.
The display can be as simple as a console application or use a full
graphical interface. Ruby Inside recently had an article about
graphical toolkits if you are interested.
Polyrhythm is the simultaneous sounding of two or more independent
rhythms.
This quiz may be worthy of a revisit in the future. Until then, here
is my solution: the beginnings of an “Annoyance” trainer.
# rhythm.rb
class Rhythm
BPM = 20
SECONDS_PER_MINUTE = 60.0
def initialize(n, sym)
@sym = sym
@seconds_per_hit = SECONDS_PER_MINUTE/(BPM*n)
@last_hit = @seconds_per_hit
@hit_count = 0
@time = 0
puts @seconds_per_hit
end
def elapse(time_elapsed)
hit = false
if @last_hit >= @seconds_per_hit
@hit_count += 1
@last_hit -= @seconds_per_hit
puts "#{"%1.3f" % @time}: #{@sym}"
hit = true
end
@time += time_elapsed
@last_hit += time_elapsed
return hit
end
end
s = '@'
rhythms = ARGV.map{|arg| Rhythm.new(arg.to_i, s = s.succ)}
delta = 0.05
time = 0
while true
hit = rhythms.map{|r| r.elapse(delta)}.inject(false) {|hit, r| hit
|| r}
print “\a” if hit
time += delta
sleep delta
end
The program will beep indefinitely, producing a sound every time the
rhythm should be struck (to the nearest 20th of a second).
Usage: ruby rhythm.rb [rhythms]
EX: > ruby rhythm.rb 3 2
1.0
1.5
0.000: A
0.000: B
1.000: A
1.500: B
2.000: A
3.000: A
3.000: B
4.000: A
4.500: B
5.000: A
Crank up the volume on your PC speaker and have a blast near your
co-workers!
configurable to train the user in any polyrhythm 2:3, 5:4, 11:17
11:17 is simply a modified 2:3, but I challenge anyone to do it with
any degree of precision at high tempo and only 2 references (2 keys).
If you can use your whole hand (as in playing a piano), it might be
easier. Scriabin, for example, would frequently throw his poor
pianist into 11:3, 9:4, etc. brief, but frequent, frenzies (see piano
sonata no. 1 in F minor).
Todd
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