Is it possible to toggle between normal and slow translation speeds?
How is it done?
What do you mean by translation speed?
If you would like to play an audio file at a slower speed then you can use an external program (such as Audacity) to slow it down.
When I first joined LingQ, all audio was at a normal, conversational speed. Now I see in every lesson in my collection(beginner French) a lecture lente (slow lecture) notation. Also, there is a directive that there is another collection available at normal speed. The audio went from almost rapid fire where I could barely understand a word to perhaps 50% of that original speed. I don’t know how to find the other collection that is supposed to be available.
Sorry. Translation speed is totally the wrong word. Should be audio.
Thanks for clearing that up 
In fact, some collections are provided by us at LingQ but many others are provided by members in our community. At the moment we don’t have any function on the site to slow down audio playback, but you are always able to download these files to your computer and slow them down with an external program. I am aware of only a handful of lessons that have 2 or 3 versions – slow, normal and fast – but it is completely up to the content provider whether or not they want to do this.
Perhaps some day we’ll have the chance to add this functionality onto the site, but for now it would be best to do it yourself.
I know of only one program to slow down audio - it’s Audacity and it’s a bit complicated. Do you have a URL to an easier one?
It appears like nearly every serious audio-video player can now slow down or speed up the media playback. You do not necessary need to use a progaram like Audacity, Helen. Examples of such players are the Quick Times Player, the Windows Media player, the VLC player, my mobile MP3 player (Sansa by SanDisk), and lots of others.
They all change the playback speed without affecting the pitch of the audio. However, the preservation of the pitch is possible only in a narrow enough range. The nature of the algorithms that keep the pitch constant is so that the voice quality diminishes significantly if one e.g. slows down the speed by just 50%.