Modartt is a French software company based in Ramonville-Saint-Agne, near Toulouse, that develops virtual instruments built on physical modeling rather than sampling. The company was founded by Philippe Guillaume, a piano tuner turned mathematician and professor at INSA-Toulouse, and released its first product, Pianoteq 1.0, in 2006. Instead of relying on recorded audio, Pianoteq mathematically simulates the physics of strings, hammers, soundboards, and resonance in real time, which keeps install sizes small (around 50 MB) and allows for deep parametric control over tone, tuning, and acoustic behavior.

The Pianoteq line spans acoustic grands and uprights, electric pianos, harpsichords, clavichords, and a range of pitched percussion and chromatic instruments such as vibraphones, marimbas, celestas, steel pans, and harps. Modartt has worked directly with manufacturers including Steinway & Sons, Steingraeber & Söhne, Bechstein, Blüthner, Grotrian, and Petrof to develop officially licensed virtual versions of specific instruments. The software is sold in Stage, Standard, and Pro tiers and runs on Windows, macOS, Linux, and iOS as a standalone application or as a VST, AAX, AU, and NKS plug-in.

Alongside Pianoteq, Modartt produces Organteq, a physically modeled pipe organ instrument with three keyboards and pedalboard. The company has a particular following among classical pianists, film composers, and laptop-based performers who value low CPU and disk footprint, MIDI expressiveness, and the ability to tweak microtuning, unison width, hammer hardness, and room acoustics in detail.

Modartt has 10 products cataloged on Equipboard, including Virtual Instrument. Their gear is featured by 13 artists, with the strongest followings in Electronic, Pop, and Rock. Notable users include Brian Eno, Alesso, and Yoko Shimomura.