# LFO & Ramps

Generate time-varying values synchronized to the beat for modulation.

## Ramp

The `ramp` word creates a sawtooth wave from 0 to 1:

```forth
0.25 1.0 ramp  ( one cycle per 4 beats, linear )
1.0 2.0 ramp   ( one cycle per beat, exponential curve )
```

Stack: `(freq curve -- val)`

## Shortcut Ramps

```forth
0.5 linramp   ( linear ramp, curve=1 )
0.25 expramp  ( exponential ramp, curve=3 )
2.0 logramp   ( logarithmic ramp, curve=0.3 )
```

## Triangle Wave

```forth
0.5 tri  ( triangle wave 0→1→0 )
```

## Perlin Noise

Smooth random modulation:

```forth
0.25 perlin  ( smooth noise at 0.25x beat rate )
```

## Range Scaling

Scale a 0-1 value to any range:

```forth
0.5 200 800 range  ( 0.5 becomes 500 )
```

## Examples

Modulate filter cutoff:

```forth
"saw" s
  0.25 1.0 ramp 500 2000 range lpf
.
```

Random panning:

```forth
"hat" s
  0.5 perlin -1 1 range pan
.
```

## Words

| Word | Stack | Description |
|------|-------|-------------|
| `ramp` | (freq curve -- val) | Ramp 0-1: fract(freq*beat)^curve |
| `linramp` | (freq -- val) | Linear ramp (curve=1) |
| `expramp` | (freq -- val) | Exponential ramp (curve=3) |
| `logramp` | (freq -- val) | Logarithmic ramp (curve=0.3) |
| `tri` | (freq -- val) | Triangle wave 0→1→0 |
| `perlin` | (freq -- val) | Perlin noise 0-1 |
| `range` | (val min max -- scaled) | Scale 0-1 to min-max |