I bought both the Alto and Soprano Selmer Concept mouthpieces in April 2015 and have been using them for all styles of music since although they are considered a 'classical' mouthpiece.  My alto is a Buffet S3 Prestige (copper body) and I loved the Concept as soon as I put it on.  At first I felt was more restricted than my old Selmer 80 'C*' - I seem to remember reading that the lay was slightly closer - but, using the same set up of an old rovner ligature with the metal reed support removed and Vandoren Classic 3 reed, I soon felt totally at home.  The mouthpiece sounds very 'smooth', expressive and improved the, already good, intonation of the instrument and speaks really quickly - facilitating fast and exact tongue work.  The Altissimo register is a dream and pianissimo low C#-Bb passages are really easy to produce.  I have no problem producing volume or power but, I imagine, the overal sound quality might be a little gentle for many 'jazz' players.  I found that I sounded more 'Paul Desmond' than 'David Sanborn' when playing at a recent Jazz Festival but, as I am primerially a classical player, this was to be expected.

The Soprano Concept felt very strange on my Yanagisawa Elimona for the first couple of days.  It is wider than a normal Sop m/piece - to aid swapping between instruments Selmer say.  My old m/piece was a Selmer 80 'B' and the lay of both is very similar.  Again, fast tongueing is simple and Altissimo great. The intonation is good and sound very 'refined and pure' although I did find that I sounded more oboe/cor anglais or even Horn so slightly changed my set up.

All things said I love both these mouthpieces.  For the classical player they are wonderful but I feel that they offer all players a chance to explore a different refined and 'grown-up' sound.  Well worth their price which, compared woth many specialist m/pieces, isn't really that much.