stihl/viking 6127.1 ZL replacing the double toothed belt or just re-synchronizing the blades

The video explains how to replace and / or remove and reinstall the double sided tooth belt on STIHL / VIKING RT 6127.1 ZL tractor mower. The video is in Croatian with English subtitles and some funny ways how to deal with the project. The app mentioned to measure sound frequencies of the belt: https://play.google.com/store/apps/de... You can use any other app for tuning string instruments as well, as long as they show the audio frequency. Note that "tuning the belt" you should do in a silent place and put the mic of the mobile phone as close to the vibrating part of the belt as possible. Then "play" your belt and observe the frequency. For inspiration see this:    • What does a double toothed belt on STIHL /...