8 note polyphonic gated synths for Sonic Pi 3. Allows keyboard input with notes of any length. Requires SP3, and powerful computer at present: not Raspberry Pi. Article at https://rbnrpi.wordpress.com/2017/08/06/8-note-polyphonic-gated-synth-for-sonic-pi-3/ video at https://youtu.be/gD-50-_dgxg

8NotePolyphonicSetup.rb

#8 note polyphony gated synth setup program
#by Robin Newman, August 2017
#Set initial states for polyphonic synth
set :vm1,0
set :vm2,0
set :vm3,0
set :vm4,0
set :vm5,0
set :vm6,0
set :vm7,0
set :vm8,0

set :cnt1,60
set :cnt2,60
set :cnt3,60
set :cnt4,60
set :cnt5,60
set :cnt6,60
set :cnt7,60
set :cnt8,60
set :on1,0
set :on2,0
set :on3,0
set :on4,0
set :on5,0
set :on6,0
set :on7,0
set :on8,0

set :use1,0
set :use2,0
set :use3,0
set :use4,0
set :use5,0
set :use6,0
set :use7,0
set :use8,0
set :lk1,0
set :lk2,0
set :lk3,0
set :lk4,0
set :lk5,0
set :lk6,0
set :lk7,0
set :lk8,0

8NotePolyphonicSynths.rb

#8 note polyphony gated synth for Sonic Pi 3
#by Robin Newman, August 2017
TouchOSC_IP="192.168.1.50"
use_osc TouchOSC_IP,9000

use_debug false
use_cue_logging false
use_osc_logging false
set :vol,0.75
set :co,100
set :syn,:tri
set :trset,0

define :setLed do |n,i|
  use_real_time
  osc "/nc/"+n,i
end
osc "/nc/synthmaster/2/1",1
osc "/nc/vol",0.75
osc "/nc/cutoff",0.5
osc "/nc/transpose/1/8",1 # equiv 0 transpose
osc "/nc/reverb",0.5

define :getsyn do |address|
  return get_event(address).to_s.split(",")[6][address.length-2..-4].to_i
end

live_loop :get_synthmaster do
  use_real_time
  b= sync "/osc/nc/synthmaster/**/1"
  if b[0]==1
    slist=[:chipbass, :chiplead,:dsaw, :fm,:mod_fm,:mod_pulse, :mod_saw,:prophet, :pulse, :saw, :square, :supersaw, :tb303, :tech_saws, :tri, :zawa]
    p= 16-getsyn("/osc/nc/synthmaster/**/1")
    set :syn,slist[p]
    puts "synth",get(:syn)
  end
end
define :book_synth do
  s=0
  if get(:use1)==0
    set :use1,1
    s=1
  elsif get(:use2)==0
    set :use2,1
    s=2
  elsif get(:use3)==0
    set :use3,1
    s=3
  elsif get(:use4)==0
    set :use4,1
    s=4
  elsif get(:use5)==0
    set :use5,1
    s=5
  elsif get(:use6)==0
    set :use6,1
    s=6
  elsif get(:use7)==0
    set :use7,1
    s=7
  elsif get(:use8)==0
    set :use8,1
    s=8
  end
  puts get(:use1),get(:use2),get(:use3),get(:use4),get(:use5),get(:use6),get(:use7),get(:use8)
  return s
end
live_loop :resetnotes do
  b= sync "/osc/nc/resetnotes"
  if b[0]>0
    set :use1,0
    set :use2,0
    set :use3,0
    set :use4,0
    set :use5,0
    set :use6,0
    set :use7,0
    set :use8,0
    set :on1,0
    set :on2,0
    set :on3,0
    set :on4,0
    set :on5,0
    set :on6,0
    set :on7,0
    set :on8,0
  end
end
define :getTranspose do |address|
  return get_event(address).to_s.split(",")[6][address.length+1..-2].to_i
end
live_loop :setTranspose do
  use_real_time
  b= sync "/osc/nc/transpose/1/*"
  if b[0]==1
    tr= getTranspose("/osc/nc/transpose/1/*")-1
    puts "tr is",tr
    set(:trset,[-12,-10,-8,-7,-5,-3,-1,0,2,4,5,7,9,11,12][tr])
    puts "Transpose",get(:trset)
  end
end
define :pdec2 do |n|
  return (n.to_f*100).round.to_f/100
end
live_loop :get_cutoff do
  use_real_time
  b= sync "/osc/nc/cutoff"
  set :co,b[0]*40+80
  puts "Cutoff:",pdec2(get(:co))
end
live_loop :getvol do
  use_real_time
  b= sync "/osc/nc/vol"
  set :vol,b[0]
  puts "vol:",pdec2(get(:vol))
end
### PLAYING SECTION BELOW ###
with_fx :reverb,room: 0.8,mix: 0.5 do |rv|
  in_thread do
    loop do
      b=sync  "/osc/nc/reverb"
      control rv,mix: b[0],mix_slide: 0.05
      puts"Reverb mix",pdec2(b[0])
    end
  end
  
  live_loop :c_synth1 do
    use_real_time
    while get(:on1)==0
      sleep 0.02
    end
    setLed("led1",1)
    use_synth get(:syn)
    n = play get(:cnt1)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on1)==1
      sleep 0.02
      control n,note: get(:cnt1)+get(:trset),amp: get(:vol)*get(:vm1),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led1",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  
  live_loop :c_synth2 do
    use_real_time
    while get(:on2)==0
      sleep 0.02
    end
    setLed("led2",1)
    use_synth get(:syn)
    n= play get(:cnt2)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on2)==1
      sleep 0.02
      control n,note: get(:cnt2)+get(:trset),amp: get(:vol)*get(:vm2),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led2",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  live_loop :c_synth3 do
    use_real_time
    while get(:on3)==0
      sleep 0.02
    end
    setLed("led3",1)
    use_synth get(:syn)
    n= play get(:cnt3)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on3)==1
      sleep 0.02
      control n,note: get(:cnt3)+get(:trset),amp: get(:vol)*get(:vm3),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led3",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  live_loop :c_synth4 do
    use_real_time
    while get(:on4)==0
      sleep 0.02
    end
    setLed("led4",1)
    use_synth get(:syn)
    n= play get(:cnt4)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on4)==1
      sleep 0.02
      control n,note: get(:cnt4)+get(:trset),amp: get(:vol)*get(:vm4),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led4",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  live_loop :c_synth5 do
    use_real_time
    while get(:on5)==0
      sleep 0.02
    end
    setLed("led5",1)
    use_synth get(:syn)
    n= play get(:cnt5)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on5)==1
      sleep 0.02
      control n,note: get(:cnt5)+get(:trset),amp: get(:vol)*get(:vm5),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led5",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  live_loop :c_synth6 do
    use_real_time
    while get(:on6)==0
      sleep 0.02
    end
    setLed("led6",1)
    use_synth get(:syn)
    n= play get(:cnt6)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    
    while get(:on6)==1
      sleep 0.02
      control n,note: get(:cnt6)+get(:trset),amp: get(:vol)*get(:vm6),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led6",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  live_loop :c_synth7 do
    use_real_time
    while get(:on7)==0
      sleep 0.02
    end
    setLed("led7",1)
    use_synth get(:syn)
    n= play get(:cnt7)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on7)==1
      sleep 0.02
      control n,note: get(:cnt7)+get(:trset),amp: get(:vol)*get(:vm7),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led7",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
  live_loop :c_synth8 do
    use_real_time
    while get(:on8)==0
      sleep 0.02
    end
    setLed("led8",1)
    use_synth get(:syn)
    n= play get(:cnt8)+get(:trset),sustain: 6000,cutoff: get(:co),amp: 0,release: 0
    while get(:on8)==1
      sleep 0.02
      control n,note: get(:cnt8)+get(:trset),amp: get(:vol)*get(:vm8),amp_slide: 0.01,cutoff: get(:co),cutoff_slide: 0.01
    end
    sleep 0.02
    setLed("led8",0)
    control n, amp: 0,amp_slide: 0.01
    sleep 0.02
    n.kill
    #sleep 0.01
  end
end #fx

live_loop :midi_on do
  use_real_time
  b=sync "/midi/**/*/*/note_on"
  if b[1]>0
    msyn=book_synth
    puts "SYNTH",msyn
    if !(msyn == 0)
      if msyn==1
        set :lk1,b[0]
        set :cnt1 ,b[0]
        set :vm1,b[1].to_f/127
        set :on1,1
      elsif msyn==2
        set :lk2,b[0]
        set :cnt2 ,b[0]
        set :vm2,b[1].to_f/127
        set :on2,1
      elsif msyn==3
        set :lk3,b[0]
        set :cnt3 ,b[0]
        set :vm3,b[1].to_f/127
        set :on3,1
      elsif msyn==4
        set :lk4,b[0]
        set :cnt4 ,b[0]
        set :vm4,b[1].to_f/127
        set :on4,1
      elsif msyn==5
        set :lk5,b[0]
        set :cnt5 ,b[0]
        set :vm5,b[1].to_f/127
        set :on5,1
      elsif msyn==6
        set :lk6,b[0]
        set :cnt6 ,b[0]
        set :vm6,b[1].to_f/127
        set :on6,1
      elsif msyn==7
        set :lk7,b[0]
        set :cnt7 ,b[0]
        set :vm7,b[1].to_f/127
        set :on7,1
      elsif msyn==8
        set :lk8,b[0]
        set :cnt8 ,b[0]
        set :vm8,b[1].to_f/127
        set :on8,1
      end
    end
  else
    if b[0]== get(:lk1)
      set :on1,0
      set :use1,0
    elsif b[0]==get(:lk2)
      set :on2,0
      set :use2,0
    elsif b[0]==get(:lk3)
      set :on3,0
      set :use3,0
    elsif b[0]==get(:lk4)
      set :on4,0
      set :use4,0
    elsif b[0]==get(:lk5)
      set :on5,0
      set :use5,0
    elsif b[0]==get(:lk6)
      set :on6,0
      set :use6,0
    elsif b[0]==get(:lk7)
      set :on7,0
      set :use7,0
    elsif b[0]==get(:lk8)
      set :on8,0
      set :use8,0
    end
    puts "In use",get(:use1),get(:use2),get(:use3),get(:use4),get(:use5),get(:use6),get(:use7),get(:use8)
  end
end

index.html

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The index.html file contains the information for the TouchOSC file named PolyphonicSynths.touchosc
To create the file from this index follow the procedure described below.
The file index.xml needs to be converted to a format which is used by TouchOSC. To do this, download the raw file and save it as index.html Then turn it into a zip file. On the Mac do this by right clicking the index.xml file in Finder, and choosing the compress option. This will produce a file named index.xml.zip Now rename this file to PolyphonicSynths.touchosc (NB touchosc is the file extension). This file can then be loaded into the TouchOSC editor which comes with TouchOSC and downloaded to the TouchOSC app running on an iPad in the usual way.