Play With Toys
by Paul Batchelor

Play with toys is a fun little patch making use of sequencing and weighted random distributions.

Tables and Variables

The only table used in this patch is called seq, used as the main sequencer. The table is generated using gen_rand, which generates a weighted distribution for randomness.

 _seq 32 "0 0.4 7 0.4 12 0.1 5 0.1" gen_rand

The patch uses a number of variables through out the patch:

• the clock signal is stored in clk
• the main trigger signal is stored in trig
• the frequency (MIDI note number) of the sequence is stored in freq
• the entire dry signal is stored in dry
• the bpm (set to 110) is stored in bpm

 _clk var 
 _trig var
 _freq var
 _dry var
 _bpm 110 varset

Clocks, Triggers, and Sequencing

After the variables and tables have been declared, it is time to set up the main sequencer. Like many patches, this starts with a clock signal. This is done using clock.

 0 _bpm get 4 clock _clk set

From the clock signal, a trigger signal is derived by feeding it through maygate.

 _clk get 0.6 maytrig _trig set

Next, the trigger signal drives tseq. tseq is set to shuffle mode, randomly sequencing through the distribution in seq. It is then biased by 60 (middle C) and assigned to freq.

 _trig get 1 _seq tseq 60 + _freq set

FM Oscillator

The crux of this patch comes from the FM oscillator described below. Here, the frequency is obtained from freq and converted from MIDI to frequency using mtof. The next argument, amplitude, is set to 0.1.

 _freq get mtof 0.1 

The trigger signal trig is used to randomly modulate the C:M ratio of the FM pair via trand. To keep the spectra harmonically related to the fundamental and not clangorous, it is important to ensure that the C:M ratio uses whole integers, so the output of trand is floored using floor.

 _trig get 0 3 trand floor
 _trig get 0 7 trand  floor

A static modulation index of 1 is used, which completes the arguments for fm.

 1 fm

The amplitude envelope of the FM oscillator is generated via tenvx. The trigger signal trig used above also feeds into tenvx. The FM and envelope signals are then multiplied together.

 _trig get 0.005 0.01 0.04 tenvx * 

Moog Saw

Acting as a bassline, a subtractive saw oscillator uses a bandlimited sawtooth oscillator fed through a moog filter. The frequency used is identical to the frequency used in the FM oscillator, but pitched down an octave to exist in the bass register.

 _freq get 12 - mtof 0.1 saw 1000 0.1 moogladder

The envelope generator in the bass patch also uses the same trig trigger signal, except that it is fed into a maytrig to make it more sparse and less overwhelming in the mix.

 _trig get 0.3 maytrig 0.01 0.01 0.1 tenvx * 

The bass patch is then mixed into everything else so far, and assigned to the variable dry.

 + _dry set

Effects

For effects processing, the dry signal dry is fed into the zita reverb module zrev.

 _dry get dup 10 10 10000 zrev drop -10 ampdb * 

To keep the mix from getting too muddy, the reverb is highpassed at 1000kHZ, leaving plenty of space for the bass instrument.

 1000 buthp 

This signal is then added back into the dry mix.

 _dry get +