DeepSeek built a browser FM synth in one session for $1.10 and 742 tool calls
keunwoochoi · x · 2026-08-04
A browser FM-synth library was built in one session with DeepSeek for $1.10
The author says fm-synthesizers.js was built with DeepSeek 4 flash 0731 in a single continuous agent session. The result was a fully working project after 3 chat turns; the remaining 6 turns were for minor adjustments.
The project page also shows an agentic build log:
- model: deepseek-v4-flash (opencode-go)
- opencode: 1.18.11
- cost: $1.10
- total tokens: 311,261,980
- wall clock: 19h 32m
- owner exchanges: 9
- agent turns: 716
- tool calls: 742
The repo itself is a browser FM synthesizer with 19 curated patches and 40 documented controls, synthesized at runtime in a WebAssembly AudioWorklet with no samples and no network access while playing.
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