Guitar reference # Chord substitutions for guitar Each page shows one substitution as the app plays it: what it replaces and why it works, the progression as written and substituted in voice-led drop 2 voicings, and the chords in every key. **Substitutions** [Tritone substitute](https://practice.graph.audio/guitar/substitutions/tritone) [Tritone sub with its related ii](https://practice.graph.audio/guitar/substitutions/tritone-related-ii) [Backdoor ii–V](https://practice.graph.audio/guitar/substitutions/backdoor) [Secondary dominants](https://practice.graph.audio/guitar/substitutions/secondary-dominant) [Passing diminished chord](https://practice.graph.audio/guitar/substitutions/passing-diminished) [Minor iv](https://practice.graph.audio/guitar/substitutions/minor-iv) ## Practice it in Practice Lab Practice any of them in every key and position, at your tempo, with a plan that adapts. Free, in your browser, no account. [Open Practice Lab](https://practice.graph.audio/)