Table: guitar_notes
Columns: string
scientific_pitch
helmholtz_pitch
interval_from_middle_c
frequency_hz

Question: What is the lowest Frequency where the Hemholtz pitch is d?
SQL: SELECT MIN("frequency_hz") FROM guitar_notes WHERE "helmholtz_pitch" = 'd'

Question: What is the scientific pitch when the Helmholtz pitch is D?
SQL: SELECT "scientific_pitch" FROM guitar_notes WHERE "helmholtz_pitch" = 'd'