The Guru Granth Sahib is structured internally by raga: its hymns are grouped under thirty-one classical musical measures, each assigned by the Gurus to specific compositions, so the text is organised as much by the music it was meant to be sung in as by author or subject, a feature with no real parallel among major world scriptures, making musical performance, not silent reading, the form in which the scripture's own arrangement makes full sense.
Many of the original raga settings the Gurus used were gradually displaced by simpler tunes easier for ordinary ragis to learn, a drift Sikh musicologists document and increasingly treat as a loss rather than a harmless simplification; a modern Gurmat Sangeet revival, centred on institutions researching and re-teaching the original settings, has worked since the twentieth century to recover and reintroduce older musical forms into gurdwara practice, treating accurate raga as inseparable from correct performance of the scripture rather than a musicological curiosity.
A related instrumental dispute runs alongside the revival: the harmonium standard in most gurdwara kirtan is a nineteenth century European import, adopted for convenience and volume, and critics within Gurmat Sangeet argue it cannot properly render the microtonal ornamentation the classical ragas require, unlike the stringed instruments historically tied to the Sikh court musicians, the rebab and the taus, a peacock-shaped bowed instrument said to have been designed by the Gurus. Some reform-minded ragi ensembles have accordingly reintroduced these older instruments in place of the harmonium, part of the wider project of recovering the original settings.