Synth. Directory is a community-driven knowledgebase documenting which synthesizers were used in music recordings. Its searchable catalogue connects artists and songs with instruments and their musical roles, such as bass, lead, pads, arpeggios, keys, strings, brass, drums, and sound effects.

Visitors can explore records by artist, title, year, decade, instrument maker, instrument, role, or evidence status, with records covering music from the 1960s through the 2020s. The site lists tens of thousands of records, thousands of instruments, artists, and people, and includes source and review information for instrument claims. Users can browse entries, filter verified, potentially supported, unverified, disputed, or wanted records, and sort results in different ways.

Synth. Directory invites its community to contribute by adding information, editing records, and submitting photos; logged-in members can update entries. The project aims to build a broad, collaborative reference for synth enthusiasts, musicians, and researchers interested in the instruments behind recorded music.

Its interface is available in multiple languages, making the catalogue accessible to an international audience