Solo is a comprehensive practice application designed to help guitarists and bassists master fretboard visualization. Developed by renowned guitarists Tom Quayle and David Beebee, this app offers four specialized training modules that target essential aspects of fretboard mastery. Users can work on learning note names, memorizing interval shapes, outlining chord changes, and practicing scales through interactive exercises.

The app's unique approach involves asking users to find intervallic functions against specific root notes, chords, or scales while providing real-time feedback through audio input. This ensures proper understanding and execution before progressing. With support for various string instruments and tunings, including 6-string guitars, 7-string guitars, and 4/5-string basses, Solo caters to a wide range of musicians. Whether you're a beginner looking to learn basic note names or an advanced player aiming to break out of scale boxes, this app provides the tools needed to transform your playing and build confidence on the fretboard.

Solo stands out with its four powerful fretboard trainers, each focusing on a different aspect of musical development. The Note Trainer helps beginners and intermediate players solidify their knowledge of note names across the fretboard. It features interactive diagrams, alternative options, and duration-based workouts for optimal practice sessions. Users can choose from multiple instrument configurations, including standard and alternate tunings.

The Interval Trainer revolutionizes how players work on interval shapes by allowing them to practice any combination of intervallic functions. Musicians can create custom interval groups or select intervals based on specific chord types or scales. The trainer randomizes these intervals and challenges users to find them against fixed or random root notes, with visual aids showing all possible positions across the neck.

The Changes Trainer focuses on improvisation skills by guiding users through over 100 common chord progressions and single-chord exercises. With 50 levels of intervallic function complexity, it maps correct intervals over chords and listens for proper execution in sequence. Advanced features include key transposition, random key changes, and voice-leading practice through single-note lines. The Scale Trainer completes the package with over 50 scales and modes, melodic sequence options, and customizable workout settings, enabling players to break free from traditional scale patterns and develop deeper understanding.