# Sliding Opts

Whilst exploring the synth and FX opts, you might have noticed that there are a number of opts ending with `_slide`. You might have even tried calling them and seeing no effect. This is because they’re not normal parameters, they’re special opts that only work when you control synths as introduced in the previous section.

Consider the following example:

    s = play 60, release: 5
    sleep 0.5
    control s, note: 65
    sleep 0.5
    control s, note: 67
    sleep 3
    control s, note: 72

Here, you can hear the synth pitch changing immediately on each `control` call. However, we might want the pitch to slide between changes. As we’re controlling the `note:` parameter, to add slide, we need to set the `note_slide` parameter of the synth:

    s = play 60, release: 5, note_slide: 1
    sleep 0.5
    control s, note: 65
    sleep 0.5
    control s, note: 67
    sleep 3
    control s, note: 72

Now we hear the notes being bent between the `control` calls. It sounds nice, doesn’t it? You can speed up the slide by using a shorter time such as `note_slide: 0.2` or slow it down by using a longer slide time.

Every parameter that can be controlled has a corresponding `_slide` parameter for you to play with.

## Sliding is sticky

Once you’ve set a `_slide` parameter on a running synth, it will be remembered and used every time you slide the corresponding parameter. To stop sliding you must set the `_slide` value to 0 before the next `control` call.

## Sliding FX Opts

It is also possible to slide FX opts:

    with_fx :wobble, phase: 1, phase_slide: 5 do |e|
      use_synth :dsaw
      play 50, release: 5
      control e, phase: 0.025
    end

Now have fun sliding things around for smooth transitions and flowing control…