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Seb Tomczak, a.k.a. little-scale, has been and is currently working on an equal-tempered, MIDI-controlled TIA.
This is accomplished effectively by turning the TIA into a beeper; like the old ZX Spectrum. A “beeper” is just a chip with audio out pins that can be software modulated. It does not use or have any hardware logic for music. In this case the TIA does, but the available logic is used to modulate a single beep into other waveforms by ascending or descending each sample manually; and then repeating that waveform at a specific rate to generate pitch. The volume in this case instead of modulating the height of the waveform is actually controlled by the TIA hardware.
Where some TIA enthusiasts love the character and its unloved design, those who hadn’t liked the TIA before now have less of a reason.