When Narciso Yepes travels, he needs two tickets, one for himself, the other for ''Mrs. Guitar.'' Mrs. Guitar - as the airlines dubbed it - is none other than the 10-string instrument that he invented in 1964 and which has remained his trademark. Yepes is something of a renaissance man - inventor, virtuoso, scholar, composer. He and the pianist Rachmaninoff share something in common: Both wrote pieces that became so popular that each finally declined to play it in public - for Rachmaninoff it was the C-sharp minor Prelude; for Yepes, the main theme from his score for Rene Clement's film ''Forbidden Games.''
Yepes - whose current national tour brings him to Carnegie Hall Nov. 24 - began studying guitar when he was six. By the time he was 13, he had learned just about all he would learn about guitar technique from a guitar teacher. The rest he learned from great musicians who were not guitarists - which makes him unique among performers.
After enrollment, at the age of 13, in the Valencia Conservatory and the winning of the Premio Extraordinario, he began studies with the noted Spanish keyboard master, Vincente Asencio. In Yepes's words, Asencio was his greatest influence, ''really a great music teacher.
''He pushed very much, and told me that the guitar was a horrible, unmusical instrument.'' Yepes goes on to recount how Asencio declared that a scale could not be played on a guitar. Yepes demurred, plunked out a staccato scale in true guitar fashion. Asencio went to the piano and produced a silken, legato glide up and down the scale. He then went to the violin, and even the flute, to further his case. Yepes was forced to agree that the guitar was incapable of producing that kind of scale. So Asencio said he must give the instrument up.
Discouraged, Yepes went home and thought and thought. And finally, after some four weeks of thinking and working, abandoning all the rules about guitar playing, he figured out a way to produce a legato scale. Asensio agreed that that was quite good. ''Here is where he was a genius,'' notes Yepes. ''Instead of saying 'you are fantastic, remarkable' he said 'very good, fine, you can play a normal scale. But can you play one in thirds?' I was obliged every time to create new things for the guitar.''
By this point in our talk, Yepes had his guitar on his knee to demonstrate how he solved these various problems. The legato, the seamless line, he was able to manufacture - in most guitar playing it remains a rapid-fire series of disconnected, plucked, notes - is astounding. And then he played a seamless chromatic scale, each tone subtlely articulated by the plucking fingers, while the other fingers slid over the frets in glissando fashion. When he challenged Asencio to do that on the piano, it was Asencio's turn to demur. Yepes pointed out that they had reached a trade-off point. Asencio agreed, and said ''Now we can talk about music.''
Other influences included pianist Walter Gieseking, Georges Enesco, and Nadia Boulanger (with whom Yepes's children also studied with until her passing). He enjoys going to concerts and hearing other artists, but with a schedule that includes 120 to 130 concerts a year (plus the travel time in between), it leaves little time for his other interests - the discovery and documentation of medieval and baroque music, a collection of 15th- to 17th-century musical instruments, reading, thinking, composing (for himself only these days).
In addition to the richness of tone that allows him to easily fill a large concert hall), one advantage of Yepes's guitar is that music can be played as it is written. Such is the expansion of his guitar repertoire that without even thinking about it, Yepes has put together programs that he simply could not have played on a six-string instrument.
Does Yepes hope to keep up his very busy schedule of recitals, duo-recitals, orchestral dates, and recordings (of which there are over 30 - his release of Falla and Lorca songs with mezzo Teresa Berganza on DG is an outstanding example of his work as an accompanist-partner)? He notes wryly that next year, he hopes to have fewer dates, the year after even less.
Yepes, a master musician and thinking man, is a learner from all walks of culture. He loves to learn. ''We lose many opportunities to learn from others because we are sleeping. I love my family. I have writing and editing to do,'' he murmurs with a gentle smile, and our time together is ended.