|Neil Young's Martin 5-18|
From 1918 to 1922 the 5-18's were braced for gut strings.
Beginning in 1923 to the present the Martin 5-18's are braced for steel strings.
The Requinto provides a soprano voice.
When compared to 19th century classic Terz instruments (actually it was not the classic era, but the romantic era), the only differences are the tunings and the Requinto tends to have the same body depth as a full size guitar.
The Requinto is normally tuned A-D-G-C-E-A. The modern Requinto is strung with nylon strings and readily available at most large music stores for a price under $500.
The little Martin Terz instrument is somewhat expensive, $3300 to $4000. Martin currently does not produce size 5 guitars.
The Little Martins sell for around $329 to $439.