The best slow down software I've found is Amazing Slowdowner. I definitely prefer it to Transkriber. You can find it HERE. The free version gives you a good idea about its capabilities, then it's not expensive to register. I love it for Old Time ancient mp3 tracks and CDs because you can change the pitch of the recording to match what your banjo is tuned to. The slowed version sounds really clear, and it's very easy to use. The usual disclaimers.

Cheers
Ray