Development of musical application especially for gamelan is important as a step to preserve gamelan as musical Indonesian heritage. One of ways to develop gamelan musical application is to generate its synthesic sound. The instruments that sounds are generated are balungan consist of demung, saron and peking and bonang consist of bonang barung and bonang penerus. The process to generate gamelan synthesis sound is done by determine the value of each instrument keys fundamental frequency and modulate generated sound using gamelan envelope model. Gamelan envelope model can be determined by doing spectral density modelling of its sounds. This research is done by developing multiplatform application of gamelan instrument that build both in desktop and mobile. The common problem of developing musical application is about audio latency that come from the devices mainly in mobile devices. The result of this research is number of audio latency can be reduced by accessing and applying native method to play sounds in both desktop and mobile platform. Also the model accuracy between gamelan synthetic signals envelope and recorded samples using the method that described in this paper are close to zero by measure it using Mean Square Error equation.