random note

Figure 1 summary

• a timebase generates bang messages
• random number zero to 23
• add 48 as lower limit
• random range is 48 to 71

Timebase

To start with we want to create a regular stream of pulses to trigger events. These are bang messages, which really just means "compute something". To get a source of bang messages we need a metronome object, [metro]. When a value of 1 appears on the left inlet of a metronome it switches on and begins to emit bangs. It will turn off again uopn recieving a 0 value. The right inlet of [metro] sets the speed, or rather the period which is in milliseconds. A toggle switch outputs a 1 or 0, so we can start and stop the [metro 300] unit. When started it outputs bang messages at a rate somewhat above 3 per second. This is the most simple timebase, just a regular stream of bang messages.

Random number

To turn the bang messages into frequencies we need to make numbers, float values that can be understood by an oscillator or other units. Each bang message recieved by [random 24] causes it to choose a new random integer number of 24 possible random values, in the range 0 to 23. We add this to a fixed value in [+ 48] so that the minimum value is 48, and the maximum value will be $48 + 23 = 71$. If you attach a number box you will see the number changing to show a different float message is on the wire. On a musical keyboard there are about 88 notes, two octaves of which covers 24 keys, so this seems like a good pitch range for melodies, starting on C3 and ending on B4.

Oscillator

Connecting this to the frequency inlet of [osc~] produces an audio signal. The left inlet of [osc~] sets its frequency in Hz or cycles per second. Both sides of the [dac~] are fed from the same [osc~] outlet so we get to hear both speakers on a stereo sound system. The patch plays loudly and low, so watch your bass bins. It doesn't produce the correct range of frequency. A range of 48Hz to 71Hz is right down in the bottom, so we must scale it for MIDI note values to produce the right frequencies.

Figure 1: random-note

A-random-note-play.pd A-random-note-play.ogg