Hi Mathias,
I'm not saying no one did tape slicing before Les Paul. Of course he wasn't the first. That's a good point. I was speaking specifically of multi-track recording, which he very much invented. Also, overdubbing at different speeds as a creative effect, which by definition he also did first since he engineered the machine that made it possible.
In addition, he invented the solidbody electric guitar. I'm not sure you can say 'he did not invent that much' when the techniques and devices he invented are probably on 90% of the records made after 1960, either in the form of multi-tracking or in the form of a solid-body electric guitar.
Chris