These are larger bodied versions of the classical guitar, used for pop, folk, jazz and dance music and fitted with steel strings for increased volume. Instruments made are usually based on classic models developed by Martin, Gibson and Maccaferri and can supplied in either 6 string or 12 string (6 course) styles. Also acoustic basses, developed and used extensively throughout Spain and South America in guitar ensembles, are available. These instruments have larger bodies and longer necks than the standard treble acoustic, and are usually fitted with 4 steel strings.  Both treble and base styles can be fitted with acoustic, electromagnetic, or piezo-electric transducers for amplification. Tuning for the standard acoustics is the same as for the classical guitar in e’ (EADGBE) which gives a scale length in the range 610-700mm, whilst acoustic basses are tuned an octave lower in e (EADG) giving a scale length in the range 840-900mm.