1) 69 months of PV generation samples down to 1 minute ending 2020-04, 1y/s. (Resampled to 60s for coarser ~5min early samples and zeros overnight.) 2) Low-Pass Filter at 500Hz with 24dB/octave roll-off (to suppress anything above 'daily' and make seasonal stand out). 3) Manually remove start/end partial years at low point approx 1st Jan each end. 4) Duplicate mono to stereo L and R, panned hard L and R. 5) Skew one track from the other ~0.25s. 6) Apply overall fade-in and fade-out. 7) Normalise to peak -3dB approx. 8) Resample from working 525600Hz to 48000Hz, yielding ~6s of audio. Note: sounds good at half pitch too (h/t Deniz E).