Specifications

converter 1.5

2000 - 2005 urr Sound Technologies Inc.
46
The following is an example of how to program converter in trigger mode, so that impulses on the left
main audio channel will trigger a note with velocity on midi channel 1.
Step 1: program the midi conversion settings
•
go to the audio parameters menu section (F3), press [F7] for the midi conversion settings menu,
then [F5] for midi data settings, and then [F6] for the main audio channels parameters.
•
type 2 for the left conversion byte position parameter, 144 for the left statusbyte (or use the page
up / page down keys to scroll until the parameter reads “note on [ch. 1]”), then type 60 for the left
1
st
databyte value, and leave the left 2
nd
databyte value at zero. This tells converter that the left main
audio channel converted value byte should be used for the 2
nd
data byte in the midi message
(representing note velocity in this case), and that the type of midi message to generate is a note on
message on midi channel 1 (by using 144 as the status byte). By setting the 1
st
data byte in the
message to a 60, we have specified the note number (middle C in this case).
•
move the cursor to the left convert mode parameter and choose trigger mode (“trigger”), then
select “no conversion” for the right convert mode parameter.
Step 2: program the audio input settings
•
press [F3] to quickly return to the beginning of the audio parameters menus, then [F5] for the audio
gate settings menu, followed by [F6] for the main audio channel gate settings menu. The three
parameters we need to check and / or modify are the “left trigger level”, “left release level”, and “left
trig decay time”.
•
the left
trigger level
parameter controls the input gate, in that the audio signal’s amplitude must
exceed this level before a midi message is generated from it. This can be set to any value from 0 to
127; however with a value of 127, audio will never be converted because 127 is the max level. With
a value of 0, audio at all amplitude levels is converted (the gate is effectively disabled). This feature
is useful to separate wanted signals from unwanted signals (ie., separate signals from background
noise, or eliminating accidental triggering from other instruments bleeding into the microphone such
as a hi-hat bleeding into a snare drum mic). This can be set at 0 for now, and adjusted if the source
being tracked requires a different setting.
•
the left
release level
parameter determines the level below which the audio amplitude must fall
before a zero-value midi message is generated (in this case, note on velocity zero which is
equivalent to a note off message). This can be any value from 0 to 127; however if set to zero, a
zero-value midi message will never be generated. Since the notes will be stuck on without a
corresponding note off – type message, converter automatically sets this parameter to 1 when the
audio channel is set to trigger mode. Raise this value higher if the particular audio source signal you
are using for the channel tends to never drop to zero.
•
The left
trigger decay time
parameter determines the minimum time window (in milliseconds)
between a trigger value midi message (in this case note on) and its subsequent zero-value midi
message. This parameter is useful to avoid rapid re-triggering of notes (mis-tracking of the audio
signal), especially if using a very small audio buffer size where the actual rise and fall of lower
frequency waveforms may be traced. Note however that this parameter can limit the minimum note
length that converter will track at a given tempo / bpm for the particular channel, and provide less
useful results. For example, the higher the number used, the fastest note length converter will
accurately track will move down from 64
th
notes, down to 32
nd
notes, down to 16
th
notes, etc. Try a
setting around 80 to start, and adjust as necessary.
And that’s it – converter is programmed to perform triggering based on audio taken from the left audio
input. This same methodology can be applied to the right channel, or any of the other audio channels.
Note that often it is beneficial to use a filter on the audio channel for conversion work rather than the full
bandwidth input audio signal, as the filters provide the ability to further separate wanted from unwanted
trigger audio impulse signals.
Additionally, you may want to experiment with the arithmetic processing that can be applied to the
trigger channel, through which one can create customized velocity response curves and the like.
An interesting way to shape the sound of the triggered midi note is to assign a different audio channel