Mouthings, the spoken language elements in sign language discourse, are typically analysed as having a redundant, one-on-one relationship with manual signs, both semantically and temporally. We explore exceptions to this presupposed semantic and temporal congruency in a corpus of spontaneous signed conversation by deaf users of Sign Language of the Netherlands (NGT). We identify specifying mouthings (words with a different meaning than the co-occurring sign), solo mouthings (uttered while the hands are inactive) and added mouthings (words added to a signing stream without their corresponding sign), and make a sentence-level analysis of their occurrences. These non-redundant mouthings occurred in 12% of all utterances, and were made by almost all signers. We argue for the presence of a code-blending continuum for NGT, where NGT is the matrix language and spoken Dutch is blended in, in various degrees. We suggest expansion of existing code-mixing models, to allow for description of bimodal mixing.