good music machine vs UltimateScale

good music machine is made for people who love a well organized library and wish the column browser was available on iOS. - Play music in your local or cloud library
- Play mp3 or m4a files in a local or iCloud drive folder
- A folder of files uses the files’ metadata to build your library.
- iCloud files can be downloaded to your device for offline play. - Supports CarPlay - Uses logical columns (genre, album, artist) for finding your music - You can search any of the lists - You can turn off the genre column - Optionally you can filter using an additional composer column for classical music (or any genre you prefer) - You can browse your albums by album art or just text If you have questions, comments, feedback or found a bug, feel free to contact me! Note: good music machine is not entirely free. 
The first 25 artists for both the music library or a folder of files are free.
If you want to use a bigger library you can take a subscription for $0,99 per year with a 1 month trial for new users. 
Using a subscription model supports future development. Terms of Use: https://www.apple.com/legal/internet-services/itunes/dev/stdeula/

UtimateScale is a music scale learning assistant. Are you confused and tired of difficult terms and complex scale structures such as Mixolydian and Locrian? With UltimateScale, you can learn by looking at a composition in staff score, directly touching a synth keyboard key on the app, listening by ear, and moving freely in key. In addition, you can learn the scale efficiently through a quiz using the Leitner System, which is famous for learning by memorization. In addition, you can upload and share comments of various scales and your own learning know-how through the Internet Archive. - Learn the scale by looking at the sheet music and listening to the sound. - The built-in touch synth keyboard allows you to learn while directly pressing the keys. - This app does not support only C key. You can transpose from C to B and see how it performs in different situations. - You can adjust the speed and octave during playback, and you can set the playback instrument as you like. - In the quiz menu, learn various scales by solving problems and using flashcards. - For quiz questions, effective learning is possible using the famous Leitner system as a memorization method. - You can share and download new scales that have not yet been discovered through the Internet Archive, scales with comments containing your own learning know-how, etc. This app is also - Support dark mode. - Compatible with both iPad and iPhone devices. - Press scales using a hardware MIDI keyboard connected via Bluetooth or USB. - MIDI keyboard is also supported in quiz mode.