Hi
Traditionally, a Sesquialtera would be 2 ranks, as you say, and normally would run through the compass as 12th & Tierce. Sometimes on early English organs you'll find a Cornet from middle c upwards complemented by a Sesquialtera in the bass.
However, in the Victorian era, the nomenclature of mixtures becomes somewhat confused, and Sesquialtera was used for any Mixture containing a third-sounding rank (and later I would guess for any mixture if the builder wanted a "posh" name!) Audsley's views ("The Art of Organ Building" vol 1 p.442-446) show just how far the stop had drifted from its origins by the early 1900's.
It just goes to show the limitations of stop lists! Looking at an organ's spec might give you some idea of the sound, but it's no substitute for hearing it in context - stops don't always do what you'd expect them to. One example is the Stopped Diapason treble on the chamber organ in my church - an absolutely gorgeous stop, but considerably quieter than you'd normally expect in an organ of that age (it's actually softer than the Dulciana).
Every Blessing
Tony
Traditionally, a Sesquialtera would be 2 ranks, as you say, and normally would run through the compass as 12th & Tierce. Sometimes on early English organs you'll find a Cornet from middle c upwards complemented by a Sesquialtera in the bass.
However, in the Victorian era, the nomenclature of mixtures becomes somewhat confused, and Sesquialtera was used for any Mixture containing a third-sounding rank (and later I would guess for any mixture if the builder wanted a "posh" name!) Audsley's views ("The Art of Organ Building" vol 1 p.442-446) show just how far the stop had drifted from its origins by the early 1900's.
It just goes to show the limitations of stop lists! Looking at an organ's spec might give you some idea of the sound, but it's no substitute for hearing it in context - stops don't always do what you'd expect them to. One example is the Stopped Diapason treble on the chamber organ in my church - an absolutely gorgeous stop, but considerably quieter than you'd normally expect in an organ of that age (it's actually softer than the Dulciana).
Every Blessing
Tony