After extensive research to improve the resonance and ensure a balanced sound, Sonor has significantly reworked the xylophone and metallophone resonator boxes. With skillful alterations of the chambers, Sonor has achieved an even more balanced and rich sound for these models. Try them and you';ll see and hear the difference. FSC pure Pao Rosa rosewood bars for xylophones and special light alloy bars for metallophones. FSC pure resonator boxes made from cross laminated birch plywood with 100% glued seams – no screws are used to hold the box together providing a more integral sound chamber. New model SKU';s will be an extension of current SKU';s – e.g.. SXP1.1, AMP1.1, GBXP1.1, AXP1.1, GBMP1.1 etc. Tuning: precision tuning by hand, in the lower range overtone tuning, in the higher range fundamental tuning is applied to all models. New models compliment all preceding models! Mix and match with ease. Many of our customers ask for assistance regarding what combination of Orff and percussion instruments to purchase for their program. We recommend more xylophones than metallophones in sets, since the ring of the metallophone can overshadow the crisp sound of the wooden xylophone. This set is one possible combination, and includes 1 each of the following Primary Line instruments from Sonor: , Soprano glockenspiel (item 203785)Alto glockenspiel (item 203786)Bass xylophone (item 203777)Alto xylophone (item 203775)Alto metallophone (item 203781) , Each instrument is diatonic and includes appropriate F# and Bb bars; 1 pair of mallets comes with each instrument.